H1-Approval Received New-Company, But Applying for B1 thru Existing-Company

[mercury72]

Hello:

I already have an offer and H1 approval notice through Company-A (Visa not stamped). I need to travel to the US through my existing company on a B1 visa (approval pending).

Three Questions:
Q1. Since i already have a H1 approval, will this create any problems for my B1 approval and visa stamping
Q2. Is my H1 with Company-A valid after i get my B1?? Can i use the same H1 approval to join Company-A??
Q3. Do i need to return to India to get my H1 visa stamped or can i join Company-A since i am already in the US?

Thanks for your assistance,
-Mercury