Devices

I believe you can only have an account active under one device. When you issue a transfer code it disables the device it was issued from.

As stated above you can only have one account active at a time. You could switch back and forth but that would require you to get a new transfer code each time which seems more trouble than its worth to me.

Downloading FGO in your new tablet automatically create new FGO account three. Why not use those new acc to do so some experiment, waifu or husbando Gacha roll or grailing unique servant like Asterios, Arash, Benkei or your other favorite servant.

Instead of switching the same account like that, why don't try the method i have mentioned above?