diff --git a/docs/4.0/components/forms.md b/docs/4.0/components/forms.md
index c69bfe2ae2..e5a568b67b 100644
--- a/docs/4.0/components/forms.md
+++ b/docs/4.0/components/forms.md
@@ -899,31 +899,37 @@ Our example forms show native textual `<input>`s above, but form validation styl
 
 {% example html %}
 <form class="was-validated">
-  <div class="custom-control custom-checkbox">
+  <div class="custom-control custom-checkbox mb-3">
     <input type="checkbox" class="custom-control-input" id="customControlValidation1" required>
     <label class="custom-control-label" for="customControlValidation1">Check this custom checkbox</label>
+    <div class="invalid-feedback">Example invalid feedback text</div>
   </div>
 
   <div class="custom-control custom-radio">
     <input type="radio" class="custom-control-input" id="customControlValidation2" name="radio-stacked" required>
     <label class="custom-control-label" for="customControlValidation2">Toggle this custom radio</label>
   </div>
-  <div class="custom-control custom-radio">
+  <div class="custom-control custom-radio mb-3">
     <input type="radio" class="custom-control-input" id="customControlValidation3" name="radio-stacked" required>
     <label class="custom-control-label" for="customControlValidation3">Or toggle this other custom radio</label>
+    <div class="invalid-feedback">More example invalid feedback text</div>
   </div>
 
-  <select class="custom-select d-block my-3" required>
-    <option value="">Open this select menu</option>
-    <option value="1">One</option>
-    <option value="2">Two</option>
-    <option value="3">Three</option>
-  </select>
+  <div class="form-group">
+    <select class="custom-select" required>
+      <option value="">Open this select menu</option>
+      <option value="1">One</option>
+      <option value="2">Two</option>
+      <option value="3">Three</option>
+    </select>
+    <div class="invalid-feedback">Example invalid custom select feedback</div>
+  </div>
 
-  <label class="custom-file">
-    <input type="file" id="file" class="custom-file-input" required>
-    <span class="custom-file-control"></span>
-  </label>
+  <div class="custom-file">
+    <input type="file" class="custom-file-input" id="validatedCustomFile" required>
+    <label class="custom-file-label" for="validatedCustomFile">Choose file...</label>
+    <div class="invalid-feedback">Example invalid custom file feedback</div>  
+  </div>
 </form>
 {% endexample %}
 
@@ -1062,24 +1068,16 @@ As is the `size` attribute:
 
 ### File browser
 
-The file input is the most gnarly of the bunch and require additional JavaScript if you'd like to hook them up with functional *Choose file...* and selected file name text.
+The file input is the most gnarly of the bunch and requires additional JavaScript if you'd like to hook them up with functional *Choose file...* and selected file name text.
 
 {% example html %}
-<label class="custom-file">
-  <input type="file" id="file2" class="custom-file-input">
-  <span class="custom-file-control"></span>
-</label>
+<div class="custom-file">
+  <input type="file" class="custom-file-input" id="customFile">
+  <label class="custom-file-label" for="customFile">Choose file</label>
+</div>
 {% endexample %}
 
-Here's how it works:
-
-- We wrap the `<input>` in a `<label>` so the custom control properly triggers the file browser.
-- We hide the default file `<input>` via `opacity`.
-- We use `::after` to generate a custom background and directive (*Choose file...*).
-- We use `::before` to generate and position the *Browse* button.
-- We declare a `height` on the `<input>` for proper spacing for surrounding content.
-
-In other words, it's an entirely custom element, all generated via CSS.
+We hide the default file `<input>` via `opacity` and instead style the `<label>`. The button is generated and positioned with `::after`. Lastly, we declare a `width` and `height` on the `<input>` for proper spacing for surrounding content.
 
 #### Translating or customizing the strings
 
diff --git a/docs/4.0/migration.md b/docs/4.0/migration.md
index 346ef84ab0..39b7dfa168 100644
--- a/docs/4.0/migration.md
+++ b/docs/4.0/migration.md
@@ -35,8 +35,6 @@ While Beta 2 saw the bulk of our breaking changes during the beta phase, but we
 
 - Sizing classes must be on the parent `.input-group` and not the individual form elements.
 
-- Due to limitations in how CSS selectors work, all buttons must be the same element (e.g., `<a>` or `<button>`).
-
 ## Beta 2 changes
 
 While in beta, we aim to have no breaking changes. However, things don't always go as planned. Below are the breaking changes to bear in mind when moving from Beta 1 to Beta 2.
diff --git a/scss/_button-group.scss b/scss/_button-group.scss
index 83234f948a..c1b826536c 100644
--- a/scss/_button-group.scss
+++ b/scss/_button-group.scss
@@ -44,46 +44,18 @@
 }
 
 .btn-group {
-  > .btn:not(:first-child):not(:last-child):not(.dropdown-toggle) {
-    border-radius: 0;
-  }
-
-  // Set corners individual because sometimes a single button can be in a .btn-group
-  // and we need :first-child and :last-child to both match
   > .btn:first-child {
     margin-left: 0;
-
-    &:not(:last-child):not(.dropdown-toggle) {
-      @include border-right-radius(0);
-    }
   }
 
-
-  // Need .dropdown-toggle since :last-child doesn't apply given a .dropdown-menu
-  // immediately after it
-  > .btn:last-child:not(:first-child),
-  > .dropdown-toggle:not(:first-child) {
-    @include border-left-radius(0);
+  // Reset rounded corners
+  > .btn:not(:last-child):not(.dropdown-toggle),
+  > .btn-group:not(:last-child) > .btn {
+    @include border-right-radius(0);
   }
 
-  // Custom edits for including btn-groups within btn-groups (useful for including
-  // dropdown buttons within a btn-group)
-  > .btn-group {
-    float: left;
-  }
-
-  > .btn-group:not(:first-child):not(:last-child) > .btn {
-    border-radius: 0;
-  }
-
-  > .btn-group:first-child:not(:last-child) {
-    > .btn:last-child,
-    > .dropdown-toggle {
-      @include border-right-radius(0);
-    }
-  }
-
-  > .btn-group:last-child:not(:first-child) > .btn:first-child {
+  > .btn:not(:first-child),
+  > .btn-group:not(:first-child) > .btn {
     @include border-left-radius(0);
   }
 }
@@ -154,32 +126,14 @@
     margin-left: 0;
   }
 
-  > .btn {
-    &:not(:first-child):not(:last-child) {
-      border-radius: 0;
-    }
-
-    &:first-child:not(:last-child) {
-      @include border-bottom-radius(0);
-    }
-
-    &:last-child:not(:first-child) {
-      @include border-top-radius(0);
-    }
+  // Reset rounded corners
+  > .btn:not(:last-child):not(.dropdown-toggle),
+  > .btn-group:not(:last-child) > .btn {
+    @include border-bottom-radius(0);
   }
 
-  > .btn-group:not(:first-child):not(:last-child) > .btn {
-    border-radius: 0;
-  }
-
-  > .btn-group:first-child:not(:last-child) {
-    > .btn:last-child,
-    > .dropdown-toggle {
-      @include border-bottom-radius(0);
-    }
-  }
-
-  > .btn-group:last-child:not(:first-child) > .btn:first-child {
+  > .btn:not(:first-child),
+  > .btn-group:not(:first-child) > .btn {
     @include border-top-radius(0);
   }
 }
diff --git a/scss/_custom-forms.scss b/scss/_custom-forms.scss
index 56093bc484..d99a86dc7f 100644
--- a/scss/_custom-forms.scss
+++ b/scss/_custom-forms.scss
@@ -225,7 +225,9 @@
 }
 
 .custom-file-input {
-  max-width: 100%;
+  position: relative;
+  z-index: 2;
+  width: 100%;
   height: $custom-file-height;
   margin: 0;
   opacity: 0;
@@ -238,49 +240,43 @@
       border-color: $custom-file-focus-border-color;
     }
   }
+
+  @each $lang, $value in $custom-file-text {
+    &:lang(#{$lang}) ~ .custom-file-label::after {
+      content: $value;
+    }
+  }
 }
 
-.custom-file-control {
+.custom-file-label {
   position: absolute;
   top: 0;
   right: 0;
   left: 0;
+  z-index: 1;
   height: $custom-file-height;
   padding: $custom-file-padding-y $custom-file-padding-x;
   line-height: $custom-file-line-height;
   color: $custom-file-color;
-  pointer-events: none;
-  user-select: none;
   background-color: $custom-file-bg;
   border: $custom-file-border-width solid $custom-file-border-color;
   @include border-radius($custom-file-border-radius);
   @include box-shadow($custom-file-box-shadow);
 
-  @each $lang, $text in map-get($custom-file-text, placeholder) {
-    &:lang(#{$lang}):empty::after {
-      content: $text;
-    }
-  }
-
-  &::before {
+  &::after {
     position: absolute;
-    top: -$custom-file-border-width;
-    right: -$custom-file-border-width;
-    bottom: -$custom-file-border-width;
-    z-index: 1;
+    top: 0;
+    right: 0;
+    bottom: 0;
+    z-index: 3;
     display: block;
-    height: $custom-file-height;
+    height: calc(#{$custom-file-height} - #{$custom-file-border-width} * 2);
     padding: $custom-file-padding-y $custom-file-padding-x;
     line-height: $custom-file-line-height;
     color: $custom-file-button-color;
+    content: "Browse";
     @include gradient-bg($custom-file-button-bg);
-    border: $custom-file-border-width solid $custom-file-border-color;
+    border-left: $custom-file-border-width solid $custom-file-border-color;
     @include border-radius(0 $custom-file-border-radius $custom-file-border-radius 0);
   }
-
-  @each $lang, $text in map-get($custom-file-text, button-label) {
-    &:lang(#{$lang})::before {
-      content: $text;
-    }
-  }
 }
diff --git a/scss/_input-group.scss b/scss/_input-group.scss
index f1d3c9dea1..7ef0267cc3 100644
--- a/scss/_input-group.scss
+++ b/scss/_input-group.scss
@@ -33,9 +33,8 @@
 
   .form-control,
   .custom-select {
-    &:not(:first-child):not(:last-of-type) { @include border-radius(0); }
-    &:first-child { @include border-right-radius(0); }
-    &:last-of-type:not(:first-child) { @include border-left-radius(0); }
+    &:not(:last-child) { @include border-right-radius(0); }
+    &:not(:first-child) { @include border-left-radius(0); }
   }
 
   // Custom file inputs have more complex markup, thus requiring different
@@ -44,12 +43,10 @@
     display: flex;
     align-items: center;
 
-    &:not(:first-child):not(:last-of-type) .custom-file-control,
-    &:not(:first-child):not(:last-of-type) .custom-file-control::before { @include border-radius(0); }
-    &:first-child .custom-file-control,
-    &:first-child .custom-file-control::before { @include border-right-radius(0); }
-    &:last-of-type:not(:first-child) .custom-file-control,
-    &:last-of-type:not(:first-child) .custom-file-control::before { @include border-left-radius(0); }
+    &:not(:last-child) .custom-file-control,
+    &:not(:last-child) .custom-file-control::before { @include border-right-radius(0); }
+    &:not(:first-child) .custom-file-control,
+    &:not(:first-child) .custom-file-control::before { @include border-left-radius(0); }
   }
 }
 
@@ -139,28 +136,21 @@
 // border-radius values when extending. They're more specific than we'd like
 // with the `.input-group >` part, but without it, we cannot override the sizing.
 
+
 .input-group > .input-group-prepend > .btn,
-.input-group > .input-group-prepend > .input-group-text {
-  // All prepended buttons have no right border-radius
+.input-group > .input-group-prepend > .input-group-text,
+.input-group > .input-group-append:not(:last-child) > .btn,
+.input-group > .input-group-append:not(:last-child) > .input-group-text,
+.input-group > .input-group-append:last-child > .btn:not(:last-child):not(.dropdown-toggle),
+.input-group > .input-group-append:last-child > .input-group-text:not(:last-child) {
   @include border-right-radius(0);
-
-  + .btn,
-  + .input-group-text {
-    @include border-left-radius(0);
-  }
 }
 
-// We separate out the button and input resets here because `.input-group-text`
-// can be any HTML element, but buttons are always inputs, buttons, or anchors.
-.input-group > .input-group-append {
-  // Everything but the last one have no rounded corners
-  .btn:not(:last-of-type),
-  .input-group-text:not(:last-child) {
-    @include border-radius(0);
-  }
-
-  .btn:last-of-type,
-  .input-group-text:last-child {
-    @include border-left-radius(0);
-  }
+.input-group > .input-group-append > .btn,
+.input-group > .input-group-append > .input-group-text,
+.input-group > .input-group-prepend:not(:first-child) > .btn,
+.input-group > .input-group-prepend:not(:first-child) > .input-group-text,
+.input-group > .input-group-prepend:first-child > .btn:not(:first-child),
+.input-group > .input-group-prepend:first-child > .input-group-text:not(:first-child) {
+  @include border-left-radius(0);
 }
diff --git a/scss/_variables.scss b/scss/_variables.scss
index b9d963e746..1c6ca3abb5 100644
--- a/scss/_variables.scss
+++ b/scss/_variables.scss
@@ -509,12 +509,7 @@ $custom-file-box-shadow:            $input-box-shadow !default;
 $custom-file-button-color:          $custom-file-color !default;
 $custom-file-button-bg:             $input-group-addon-bg !default;
 $custom-file-text: (
-  placeholder: (
-    en: "Choose file..."
-  ),
-  button-label: (
-    en: "Browse"
-  )
+  en: "Browse"
 ) !default;
 
 
diff --git a/scss/mixins/_forms.scss b/scss/mixins/_forms.scss
index ba1b16d6a1..d25df182df 100644
--- a/scss/mixins/_forms.scss
+++ b/scss/mixins/_forms.scss
@@ -88,11 +88,18 @@
           background-color: lighten($color, 25%);
         }
       }
+
+      ~ .#{$state}-feedback,
+      ~ .#{$state}-tooltip {
+        display: block;
+      }
+
       &:checked {
         ~ .custom-control-label::before {
           @include gradient-bg(lighten($color, 10%));
         }
       }
+
       &:focus {
         ~ .custom-control-label::before {
           box-shadow: 0 0 0 1px $body-bg, 0 0 0 $input-focus-width rgba($color, .25);
@@ -105,13 +112,19 @@
   .custom-file-input {
     .was-validated &:#{$state},
     &.is-#{$state} {
-      ~ .custom-file-control {
+      ~ .custom-file-label {
         border-color: $color;
 
         &::before { border-color: inherit; }
       }
+
+      ~ .#{$state}-feedback,
+      ~ .#{$state}-tooltip {
+        display: block;
+      }
+
       &:focus {
-        ~ .custom-file-control {
+        ~ .custom-file-label {
           box-shadow: 0 0 0 $input-focus-width rgba($color, .25);
         }
       }