It works on N3ds, 2ds and 3ds. Go to www.3dbrew.org for the exact details.
I guess it would be possible to play an out-of-region gamecard online. Not sure about it but you could give it a try
Only if the game doesn't have updates, you'll need 9.2 or below to install out of region updates as CIA.
It seems like most games with online receive an update at some point, often right after release, so it's problematic.