H1-B transfer while HI-B extension pending

[loku]

I been working on H1-B for sometime. My project ended 3 months ago and I had been unpaid since then. My H1-B expired on Sep 30, 2009. My company applied for H1-B extension in June but got a RFE due to lack of evidence. Cmpany replied to the RFE. The status has been pending since then. On Sep 19, I got an offer from another company. The new company filed for premium processing for H1-B transfer and the transfer application got approved with starting date of September 24. I haven't got my new approved I-797 yet.

I joined the new company on Sep 29 but haven't notified her old employer yet and hence they didn't withdraw my application. My immigration is underway and I have got an approved I-140 from my previous employer. That is the reason I didn't notify them as I don't want to stop that process. It is my intention to move back to my old employer if my visa extension is approved so that I don't have to refile for Green card.

Now the question is what will happen in these scenario and purportedly 'Last Action rule' of USCIS:
1) If my Visa extension gets accepted, which VISA will hold good, the H1 ext with original employer or H1-B transferred visa with new employer as the H1-ext will be the last decision by USCIS ? Where should I report for work. Can I chose among these two employers who I want to work for?
2) If my visa extension gets rejected, will my transferred VISA still hold good ? Will I need to do anything in that scenario i.e. need to go out of country and get my visa stamped ?

What is my best course of action.

Any help will be really appreciated.