no need to answer all at once
Grunfeld: pawn sac!

This is considered to be the most instructional game in this variation: http://www.chessgames.com/perl/chessgame?gid=1302450

From the viewpoint of Black:
Your plan is obvious: you have two connected passed pawns on the a and b files. Promote one.
In the meantime White is probably going to drum up some sort of initiative he'll claim is somehow compensation for _two_ _connected_ _passed_ _pawns_ (as if), and at some point you'll probably need to spend a move or two defending against that.
This is considered by many to be the main line of the entire Grunfeld Complex:
What are my plans as black against, and what lines should I play?