align container in center bootstrap code example

Example 1: bootstrap 4 center div

<div class="d-flex justify-content-start">...</div>
<div class="d-flex justify-content-end">...</div>
<div class="d-flex justify-content-center">...</div>
<div class="d-flex justify-content-between">...</div>
<div class="d-flex justify-content-around">...</div>

Example 2: align eliment in center of row bootstrap

<div class="row justify-content-center">
  ...inner divs and content...
</div>

Example 3: how to center vertically in bootstrap col

<div class="my-auto">
  ...inner divs and content...
</div>