What if you want to restore data from an old phone with a different number?

The data on your phone is not tied to your phone number. Here is a support article on transferring data—>Transfer data from your previous iOS device to your new iPhone, iPad, or iPod touch - Apple Support

Expanding on my reply, there are things (not data) that is tied to your phone number. You need to log out of iMessage and FaceTime, which have your phone number, and also any messaging services that use that number like WhatsApp, Signal, Telegram, Google Duo, etc.

Also, if you have 2 factor authentication enabled you need to add the new number as a trusted number while the old number is still active.