Not my system of choice but used a good few over the years they're functional.
Powermaster is all 2 way, not the same as the discontinued Powermax.
I believed ADT had custom firmware after they took on Visonic, so doesn't default to the off the shelf codes.
If that's the case looks like you'll need ADT to reinstall everything, expensive mistake following random stuff online...
You can enroll/delete keyfobs from the master user menu it's not an engineer/installer only function.