Question about Shelly 1PM Mini Gen3

2 times yes. The "Timer" function can be used to programme after how many seconds the device should be switched off after it has been switched on. And of course you can install the app on several mobiles, log in with the shelly user account and then switch the device.
If the radio receiver on the door operator is to be replaced by a shelly, try out beforehand (e.g. with a button) how the direction reversal (open - stop - close - stop) works.
To be on the safe side, install an RC element in parallel to the motor and have an emergency opening (cable pull, door entrance, etc.) ready so that you are not permanently locked out if the shelly loses its programming (it happens!).