And I haven't played any Pokemon games since R/B/Y, so I'm learning everything from scratch. And I haven't tried any of the online elements, yet, except I went underground for a while but there was no interaction with anyone. I've only gotten two badges so far. When do you get the National Dex anyway? I've heard you have to fill up the Sinnoh Dex first? That would be awful. I never even filled the R/B/Y Pokedex (I had 12 Mews, but could never find people to give me like, 3 that I needed that weren't in my game).
(Whoo, I feel 11 again.
)
Nah, the Underground is only for local players only, which sucks -- but you can dig up quite a few nice things down there, so going alone is totally worth it.
And yeah, you unlock the National Dex by completing the Sinnoh Dex -- but in these games you just have to see the Pokemon in order for it to count, not catch them, which makes it a LOT easier than the other Pokemon games. You can actually see all of the Pokemon in each version, so you don't have to trade with anyone to get the National Dex. If you want to catch them and have a nice little definition, then you might need both versions / use the GTS.
Yeah, I needed, like, 2 in my Red Version.