As far as I know, the QR code is only for logging in to the web chat (or desktop version, I guess).
It’s possible there is a way, but I looked into it and couldn’t make it work. Feel free to try yourself, but this conversation’s turning into an unwanted argument and I’m out.
You’re downvoting and calling me wrong based on 30 seconds of research, so I’d say you are the instigator.
The backups in Google Drive are not accessible to you. The source you found doesn’t contradict me, because it doesn’t mention being able to access that backup, only delete or disable them.
You can only transfer your account, which doesn’t test the backup. Getting to the stage where you’ll be able to test the backup leaves you not logged in. The backup process needs a SIM.