I'm making a mobile game and had the idea of using transfer codes for taking one account to another device.
Lately, I've seen this function being used in a lot of mobile games, you go to the game settings, issue a transfer code, input it in the new device and the game account is transferred. However it's not clear for me as to how this works? since many games I have seen with this function can't transfer premium currency between different OS, for example. Or some of them, after transferring the game disable the old device from transferring back the same account before certain time has passed.
I have been looking for some information about this system but haven't been able to find out anything. So I was hoping if anyone could point me into the right direction, specially in the point about currency transfer between different OS.
Edit: I'll try to be a little more clear about the issue. I want to have a feature where the user cas generate a code to transfer his account or progress to another device, that's it.
The other question I had was because this kind of systems do exist actually. Mostly on games developed in Asia. They allow you to transfer your progress this way to any other device BUT if you do this from one OS to another normally you can keep your progress intact but not the in-game currency. So I was wondering why