Regarding H1B Extension

Hi ,

My H1B Visa willl expire on this September 2014(I 94 also expires on Sept). Currently I am in US. My employer [b]has not[/b] initiated the H1B-extension yet. My questions:

1. After September (expiry), how long can I remain in US and work?

2. If current employer files H1B extension before this september, is it allowed to stay in US after september with this filed status. 

(a) If yes, what are the documents need to keep in custody(as proof) if staying in US after sepetember.

(b) If H1B extension has got approved status, shall I need to return to India for stamping again or  can I continue work in US and stamping only required whenever I return from US?

2. Is it possible to transfer h1b now and the new client can apply for extension ? In this case, is the H1-transfer and extension are two different process or can be done together by the new client?

Thanks in advance. Waiting for your reply.