I'm pretty sure that nobody who says that the browser exploit works on 2.1 has tried to use it on 2.1. There is an exploit web page for 2.1, but the browser exploit runs by automatically starting up more exploits and those other exploits don't work on 2.1. You'll need to either get a game and update to 4.1-4.5 and use the profile exploit, get a game and update from 5.0-9.2 and use the browser exploit, or get a game and update from 5.0-9.2, use the browser exploit once, then downgrade to 4.1-4.5, and use the profile exploit.
As fdr the two SDs, the two SDs are for different things. The Gateway cart has a micro SD to hold games, your 3DS also has a normal SD and Gateway uses that for EmyNAND and saves.
EmuNAND allows you to run an older firmware, but have an emulated newer firmware, so you can play newer games.