I filed for h1b this year and UCSCIS responds with RFE.
What to do next?
what is the probability of approval and rejection?
How long it gonna take and if it got approved afte 3 months on December 2012, can I work from January 2013 or have to wait till October 2013?

Please suggest.

Thank you very much

 What to do next?

Make sure you reply with strong and precise documentation. Check with your attorney.

what is the probability of approval and rejection?

It depends on the case and what they have requested in the RFE. The probability of approval is high. If it were to be rejected, they would have not asked for RFE.

How long it gonna take and if it got approved afte 3 months on December 2012, can I work from January 2013 or have to wait till October 2013?

If you did not pay premium processing, then it will take 3 months for them to review your reply. You can start working as soon as it gets approved.

However, you can always pay the premium processing now and have your application reviewed sooner. You can pay the premium processing $1225 with your reply which will ensure that they will review your reply within 15 days. If you have sent them the proper documents, your h1b should get approved within 20 days, and you can start working on 10/1/2012.

Thank u very much BigOne.. I indeed appreciated it.

Hi Playboy,
You got RFE and why you got it? It's pretty much clearly written in your RFE and the necessary steps to taken before it gets delayed. You didnot mention here why did you receive and asking for 'what to do next?' seems little odd questions to us. Please read your RFE twice, thrice, it's written the reason for RFE and the supporting documents USCIS is looking for the RFE. Talk with your company HR and your company lawyer who filed your H1B, and make sure its company's supporting documents that is missing while filing H1B. (I do not know if it's ur first time B1B or H1B estension).

Once you submit all the required documents as needed by USCIS (these documents are critical, it should be exactly the same thing USCIS is looking  for in RFE, OW chances of rejection is high. Pls dont take it otherwise, if not seriously) and submit before the deadline.

As far as premium is concerned, I am pretty sure that once you get RFE, there is no point for applying for the Premium processing (they will not even accept the premium processing after RFE.) . However, once you submit the RFE with all documentation complete and strong covering letter from the employer, you will get approval within the next 2 weeks, maximum of 14 days. So good luck and just prepare documents as asked by USCIS and submit ASAP.

playyboy,
just to give u an idea...... mine took a year to get approval.
was working for cunsulting company in project - march 2008.
filed h1b - april 1st 2008 Regular processing.
received notice in 1 month.
june/july 2008 - RFE (how does gradaute degree relates to his work).
aug/sep 2008 - send RFE docs to USCIS
nov 2008 - asked consulting company to do PP. They said they did, but since they couldn't provide with denial or approval USCIS return money. ( now today I doubt this, i dont think they applied PP).
Project finish 31 dec 2008.
OPT expired - 2nd week of Feb 2009
Joined Kaplan march 2009 (there was no cap gap rule at that time)
End week of April 2009 - Got approval stating 2nd week April 2009 - Aug end 2011.