I am a F-1 student on OPT extension working with Company A. Company A has applied for my H1 visa in Mar'09 and the current status of my visa is "Post-Decision Activity On April 23,2009, we mailed you a notice that we have approved this I129 PETITION FOR A NON-IMMIGRANT WORKER

Now,my Company has decided to cancel my H1 & mailed a request to USCIS for cancellation on Sep 25,2009 and according to Fedex tracking number, it has reached them on 28th Sep'09.

1) How much time does USCIS take to cancel my H1?
2) Will I be out of status if USCIS doesn't cancel my H1 before October 1st 2009?
3) What can I do, to not loose my OPT Extension status and to prevent H1-B from kicking off on Oct 1st?
4) Does the change of status takes place immediately from OPT to H1 on Oct 1? How does this work?