I work for Company X as a permanent employee and have my I-140 approved in EB3 category from company X with a priority date of Nov 2009. I have my H1B extension for 3 years based on my I-140 approval till Dec 2013. I am planning on moving to company Y.

1) What will happen to my H1B extension (till Dec 2013) if company X, who are the original sponsors of my I-140, revokes my I-140 before my labor from company Y is approved (under EB2 category)? I am told that since my H1B was purely extended based on the I-140 approval from company X, my H1B lapses as soon as my I-140 is revoked by company X. Is this true?

2) If my visa is stamped through company X till Dec 2013 and if I join company Y, can I go to India and come back to the US without going for stamping till Dec 2013?