Is H1 Transfer Possible if passport not stamped


I got H1B approved till 2015 in FY 2012.It was a change of status from H4 to H1.Due to some medicial emergeny,I had to travel to my country before Oct 1,2012(the date my H1 visa starts).

Now,the client is not ready to extend the job offered to me and they withdrew the offer.


1)Is it a possibilty that I can take a different client letter and appear for H1 visa Interview or I should take the same one which was applied with my petition?

2)Is H1 Transfer an option?Can i get the transfer done even before i started working in United States??