FWIW the leaked version was a cart rip which had version string 0. People have been speculating that the v0 is the reason people got banned, but it's more likely the fact that there was a fuck ton of users on the servers before the game was supposed to be released and they log connections...
I can go into settings and begin a new NNID setup, but I don't want to do this just yet. Having an NNID tied to the system and nuking it also removes all games and updates installed via the eshop, so if I don't want to have to reinstall game updates etc if I end up having to circumvent the eshop...
Kind of. It's only disabled for those with NNIDs. Injecting an all-zero nnidsave.bin will give you eshop access again (minus your account, obviously). Evading the online game ban is currently not as simple, but can be done.
fwiw here's some pictures
This error is actually just a generic indicator of online features being suspended. You are at the mercy of Nintendo in regards to the actual duration of this ban.