You are going to need to likely get ahold of your friend and their console, and log back into your NNID as its linked to their console on nintendos servers and do a system transfer back to yours to get it moved back. Just a system format isnt going to bring your NNID back to your console without issues without the transfer.
Unlinking the system in this case unfortunately is with a transfer. Just logging in and out would still have the console linked on nintys server and wont remove it as you are wanting. In this case, yes it is a kind of a pain, but its whats needed.
No. You need to do a system transfer, as the only way to remove an NNID without formatting is to delete the NNID entirely.
It would only log you out on a console level. A transfer is going to log you out fully of the console and of nintys servers. If its done as it is, you have and will see that when you connect to say, the eshop, it will give a error that the NNID is on a wrong system and that games and dlc you have bought before will likely be lost as it tries to correct itself as that NNID shouldnt be on that console when it commutes with the servers.
it is both my consoles, so i dont mind about the nnid.. i can just make a new one if necessary.. my concern now is how to restore the source console....
