1) Perhaps. I can't remember if there are any PAL Netlink games or not, but they would not compatible with the NTSC versions. At the very least, you need the ability to play the NTSC Netlink games, which means either buying an NTSC console or finding a way to play imports on your own system that doesn't require the cartridge slot. If you have a PAL console, I believe the only solution is modding the system... I don't think a swap trick will work well enough.
2) The Netlink will work in a console from any region, but the games won't. You'll need the NTSC versions of the games to play with the rest of us. Sorry.
3) For the same reasons I listed above, I don't believe it's possible to connect a PAL version of the game with an NTSC version of the game. (There would most likely be an issue related to the different framerates... the Netlink's synchronization methods are tied into this.) A console can be changed to believe it's from a different region, though.
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I have my Saturns, I have some of my games, I have a RasPi. Gotta put all this stuff together!