About account transfer code

had to issue a new one after a transfer, other than that its always been the same, just keep a copy of it on another device or a cloud other than the one you use to play FGO and you will be fine

No. There is no need to do that. It doesn't matter how long the transfer code is as long as you have a copy of it and remembers the password, you're good. Got a problem with my app yesterday and my transfer code months ago still worked.