H1-B Transfer based on approved I-140

[awaitinggc]

I am in 5th year of H1-B. I have I-140 approved with Employer A and got 3 years extension based on the same. I am planning to switch jobs and join Employer B. Here are my specific questions

1. Would I be able to get 3 years extension based on I-140 approved with Employer A? I think answer is yes here. Though Employer A did not give me any documentation for I-140 approved. All I have is a case number for my I-140 filing and case number for approved LCA for Perm. Would that be sufficient enough to get 3 years H1-B with Employer B?

2. Can I keep getting 3 years extension of H1-B with Employer B based on approved I-140 application with Employer A? I know that Employer A does not cancel I-140 application. Note that I do not have documentation of approved I-140 application except the case number

3. Since I already have 3 years extension on H1-B with Employer A and if I transfer to Employer B based on that, what could be possible validity of new H1-B? Would it be 1 year since only 1 year was remaining on original H1-B or would it be 3 years based on new H1-B petition I received from Employer A?

4. Since I already have 3 years extension on H1-B with Employer A and if I transfer based on that, how soon should Employer B start green card process? I have heard that it has to be filed before last year of H1-B, but want to confirm the same from experts here.

5. If Employer B files greencard, can I port my proirity date? I think I can if I have I-140 approval documentation. But can I port without sufficient documentation. Would case number be enough for porting priority date?

Thanks in advance for your help