xiaobaitu's answer for your question about GC

Usually it's normal if you may get the result within 6 months since you took an interview,except the background investigation still no yet.I suggest that
you should write to your local INS office after a few
months,or go to there to inquire about your case,if you
still never receive any new information.You were scheduled an interview mean that your case had been tranferred to local INS office,as our previous experience ,you can't get information from website & telephone system of INS if your case is pending at local INS office.And for the offiecrs of local INS,usually they wouldn't like to answer your questions
on the phone,you'd better write or go to there.