Drupal allows configuring explanation and submission guidelines for each content type. How to display those on a custom route ?
How to rename uploaded files with programmatically generated random names on Drupal 8/9.
How to programmatically create a dynamic menu link (and pass it an argument).
How to implement custom views data on Drupal 8 and to join the user table to the query using hook_views_data(). Making a relationship between a user uid and the user table to finally get a fully loaded user object.
In this tutorial we will see how to implement a custom form template in drupal 8. Implementing custom form template is a basic if you want to get fully customizable HTML code and make a lot of sens if you are working with toolkit such as bootstrap.