About removing two years green card condition_please answer it

Hello,

I file removing two year green card condion by marriage green card last year May.

Feb 2012, I receive the letter from USCIS, they need further document. I mail the other documents on Mar 2012. How long I have to wait to get green card approved?

The one year extention letter will be expired on Aug, if I can continue to work after Aug when the green card case is pending?

if I can apply for citizen on 2 years 9 month fromt the first green card I received when the green card case is pending?