Hmm no, I use this from time to time, and it really is just a way to copy the codes to another device. It won't delete them from the original device. It notifies the device owner after a few minutes that the TOTP have been exported, and it keeps a log of exports.

I'm in the process of moving to Aegis. It's FOSS, encrypts the file on the device, and supports the biometric lock. It can do a daily backup to a few sources, including the Google backup (I think) and personally I dump it to a folder that my Nexcloud will automatically upload to my personal server.

It doesn't delete them from the existing device. However, it exports them via qr code, which it prevents you from screenshotting, meaning you can never factory reset your phone or protect yourself from theft or loss. You can only transfer to another phone when you have both devices working at the same time.

Not on iOS within the last year or so.

What you are suggesting is technically impossible.

You'd need to involve the provider for changing token seeds.

At a client level, all you have is one seed.

If you save a seed, it can be used on any number of devices.