Change of employer with approved I-140

 Question:  I have immigration questions. Could you please help me. I have an approved I-140 in EB2 category (filed by current employer A) in year 2014. Now I am planning to move to employer B (end-client from my current assignment). Questions: 1. If the current employer A withdraws approved I-140 after I transfer H-1B to company B and I don’t have an approved I-140 from employer B, can employer B request for another H-1B extension based on approved I-140 from employer A? Question 2. If the current employer A withdraws the approved I-140 after I move to company B and if I want to later come back again to employer A, is there a possibility for employer A to convert the I-140 application again back to Active status which was previously withdrawn in order to apply for I-485 when dates are current. (or) Employer A has to again start with applying the new PERM and I-140 applications. Thanks for all your help.

Answer: To use I-140 for extensions beyond 6 years, the I-140 must have been approved for at least 180 days. Further, if your previous employer withdraws the I-140, they will have to get another PERM and I-140 approved to enable you to file I-485.