I work currently for Company A. I got offer from Company B. A files for H-1B extension and B files for H-1B transfer petition. Both are timely filed before my H-1B visa expires. I got H-1B transfer approval for B now before visa expires. But current company A extension petition is still in processing. I wanted to know :

1. If I start working for Company B, will there be any impact on Company B approved transfer petition because of A extension petition as both I suppose will have same I-94 number.
2. What if my current employer do not withdraw my extension petition even after I join Company B and later what happens when A extension petition gets denied or approved?

I will appreciate opinion on above situations. Thank you