H1B transfer 7th year with approved I-140

[phoenix2010]

I'm in 7th year of H1B with approved I-140 from employer A. I want to transfer my H1 to employer B.

 

1. Can my new employer asks for 3 years extension during H1 transfer with my I-140 from old employer?

2. Should the job profiles match exactly if my new employer wants to port my old priority date? 

3.If my present priority date becomes current after I move to new employer, can my old employer file I-485 for me as future employee? If yes, should I move back to my old employer after Green card is issued.