The problem is that you didn't unlink your NNID before downsgrading. Either upgrade and unlink then downgrade again (higher chance of brick, just because you have to do the process again), or update your emunand to 10.3 and link it.
Though, there really isn't a need to link your NNID back anyway. If you want to redownload games on the ESHOP you already own them and can probably install them by other means.
The friends list is linked to the device, so it works all the same. All the NNID does is allow you to get on the ESHOp really.
You can't spoof them, why would you even need to?
Edit: Though, apparently Smash requires a Nintendo ID to play? Can't confirm that.
Also, you can't be linked on sysnand and emunand, since they're treated as separate devices. You'll need to use 2 NNID
