I am currently in USA on L1 visa valid till June 2010 through company A. I have approved H1 from company B that will come into affect from October 2009.

Can I travel to India on L1 and comeback on L1 before October 1st? What will happen to my H1 in this case.
Can I travel to India on L1 and comeback on L1 after October 1st? What will happen to H1 in this case.

I don't want to get H1 stamped in either of the above two cases and want to continue on L1. Is that possible. If yes, if I want to change to H1 later, can I do that?

Thanks