Unless your screen is on your watch face, the AOD will always default to a standard digital clock unless it’s tracking a workout or something like that

Nope, the phones get out on a non pay blacklist so they can’t be reactivated

Either stolen or fraudsters who set up carrier accounts, selling the devices they can get and not paying the bill which will cause the phone to become useless at some point

Go to settings, general, about, tells you the model name of the phone on the top of that page