What all additional domain name extensions do you register with the primary?

What all additional domain name extensions do you register when you are registering your primary domain?

For example, when you register mynewapp .com do you also register/reserve
mynewapp .ai
mynewapp .io
mynewapp .co
mynewapp .app
etc etc extensions?

What are all the main benefits of registering these additional extensions apart from someone else not copying ours?

How can we use them to improve our main domain reach or get more customers?