1. With my approved I-140 from Company B can Company C use that to file my extension for 3 years. I have a copy of approved I-140. Is it safe to change companies in the 6th year.
2. Using the approved I-140, I have filed H4-EAD for my spouse in Feb 2017 and is yet to receive the EAD approval. If I get it will be only valid till Nov 2017 based on current I-797 validity. So, if H1-B is approved for Company C, can I file extension of H4-EAD 120 days before validity based on that approval. If EAD is provided, it is going to expire on Nov 2017 based on the H1-B's current I-797.
1.Yes you can file for an extension. That's all you need a copy of the approved I-140. It is safe to change companies. The law is once your I-140 is approved and stays approved for 180 days, even if your old employer revokes your I-140 you have the right to keep extending your H-1 through any employer.
2. I think you can apply 180 days. The new regulations allow you to file for EAD extension 180 days ahead of time. Have it double checked. It is not a guaranteed right but USCIS has said that they will accept that unless they post it differently on their website. So always double check the information. More...