And to enlighten even further
Once your account is set up ensure you note the password. Getting account password reset is a real pain so take heed
Initial bind of account to car
All you are doing is using a phone with the app to link the car vin (via the QR code) with your account to initialize the account connection to the car.
One car, one account, one user id (email), one password only
The initial set up phone is not locked to the "bind" it is/was merely a tool to set it up.
You can only do the "bind"/link process once. Once done you will not be presented with a qr code again as the car is already linked to an account.
You can use multiple devices with the app loaded to communicate with the car using only the same account user ID (email address) and password you set up initially. This helps, for example, if you are a new phone every year type of person, if your phone is lost/stolen/dies on you, or having two or more drivers sharing the car
Only one active user can communicate with the car at any one time. Any new device logins will force out the current/active/previous login.
There is no method of checking any problems at the MG infrastructure end as of yet. You may experience communication problems occasionally without any clear reason, remembering you need to be in an area where the cars esim can get a good signal in the first place.
The cars communication can currently can go to sleep occasionally, you need to physically unlock the car etc.to reactivate it.