Answers for "bootstrap 3 input field design"

large input box bootstrap 4

.form-control-sm
.form-control-lg

bootstrap input file

<div class="custom-file">
 <input type="file"  class="custom-file-input" id="inputGroupFile01">
<label class="custom-file-label" for="inputGroupFile01">Choose file</label>
</div>

bootstrap input tagsinput

<select multiple data-role="tagsinput">
  <option value="Amsterdam">Amsterdam</option>
  <option value="Washington">Washington</option>
  <option value="Sydney">Sydney</option>
  <option value="Beijing">Beijing</option>
  <option value="Cairo">Cairo</option>
</select>