Can I do H1-B transfer under a pending H1-B extension

Withdraw extension after transfer is approved ??

Company A, ( holding my current visa) has filed for an extension for my H1B ( visa expired March 2006 ..not 6th year extension). They have got a
receipt from INS and may get approval in Aug/Sep 2006.

Now I got a job offer from Company B

What happens if company A withdraws H1b extension AFTER company B's get approved ?

Will I be out of status if above happens ?

Company B's H1b transfer approval means automatic extenion approval as well ?
H1B Travel when Application Pending with USCIS

Travelling while your H1-B application is pending approval is risky. I do not recommend to travel unless you have a real emergency to go out of USA especially when Amendment is pending. We recommend upgrading your H1-B application to premium and get approval within 15 days before travelling to be on absolute safe side.

H1B Travel Allowed US Entry Risk

Amendment Yes May be denied if started working with H1B Amendment.
Extension Yes No entry without Valid H1B stamp.
Change of Status Yes No entry without valid H1B or non-H1B Visa.
Transfer Yes No entry without Valid H1B stamp.