Sure, and I think that would send a message to all of your contacts that a new account is using that number, but I’m honestly not sure. If you have an active account (i.e. on a desktop or something), I think you can just change your number if that happens (i.e. get another temp number).

It’s certainly more convenient if you use a longer-term number, but I think it’s feasible with a throwaway number. Once your account is set up, Signal doesn’t need your number for anything if you disable publishing that.

You need to enter your Signal Pin, otherwise you will get removed from all groups etc