To set rounded border to input box, use .round class and
to set square border to input box, use .sqaure class alongwith .form-control class.
To make label in center of form-control, use .col-form-label class with <label> element. This is default bootstrap class.
For Flating Label Inputs, need to use .form-label-group class & add attribute disabled for disabled Floating Label Input.
For Input Box with icon use .position-relative class with .form-group and use class .has-icon-left class for icon on left side.
For different sizes of Input, Use classes like .form-control-lg & .form-control-sm for Large, Small input box.
You can indicate invalid and valid form fields with .is-invalid and .is-valid. Note that .invalid-feedback is also supported with these classes.
Use .needs-validation with <form> for Input Validation states with tooltip, .{valid/invalid}-feedback classes for .{valid/invalid}-tooltip classes to display validation feedback in a styled tooltip.