EB2 Green Card

I got I-140 approved and also got EAD with EB2 category in April 2012. I need to change my employer but my employer did not give me my green card paper like I-140 approval copy, labor code etc. I have only receipt copy of I-140 and I-485. I heard about USCIS form G-884 (Returns of original documents) which use to get all green card documents from USCIS. I have following questions to ask you. Based on G-884, can I get my all green card
documents from USCIS without knowing my employer?

I am currently on EB-3. I have a company (say Company A) which is willing to file for my GC in EB-2 under 'Future Employment'. Do I or the 'company A' need to be aware of something on this front?

I got my green card base on EB-2 category. I got mail from USCIS mentioning they change my status in to Permanent resident. As well as I got my Green Card in mail this year March. But I filed my I-485 last year July.I want to change my employer. (New Employer offering similar salary as well as similar position ). Is there any legal issue. Do I have to worry about this junction ?

My I-140 was currently approved but the company is keeping the Original copy of I-140 approval with them, also they are not giving me the copy of original. The GC is filed in EB-3 and I have US masters degree and technically qualify for EB-2 category. I was waiting to get my I-140 approved and H-1 filed so I can start looking for change of job who can file in EB-2 with same PD.<br>
How important it will be for me to have the original copy of I-140 or how are the other ways which I can obtain this from the USCIS directly?

I am in a very difficult/complex situation, the situation is as below:<br>
Have been on H-1 for 3 + 3 + 3 + 1 years (last 4 years extended based on approved I140). Have approved I-140 with priority date of June 2010 in EB-2 category. H-1 extension was denied last year hence had to leave employer A, now I am on H-4 and will be soon filing H-1 with employer B. I have following questions on which I am requesting your opinion. <br><br>

Q1. When my priority date becomes current and if I am still with employer B, can employer A still file my I-485 and that way I can then get the EAD and join him on EAD? :<br>
Q2. Further, do I have to be working with employer A on an active H-1 visa to be eligible to file EAD when my priority date becomes current? :<br>
Q3. If question 1 approach works, can I then continue to work with employer B and employer A can process my green card in parallel. :<br>
Q4. What are the risks in working for employer B when my I140 is with employer A. Note that employer A is willing to preserve my I-140 and process green card eventually without me working for him, because he is unable to find me any projects? :<br>
Q5. I do plan to file for a new GC with employer B but worry is the priority date is likely to become current before I complete GC process with B. :<br>
Q6. Do I need to be with employer A for my wife to apply H-4 EAD based on my I-140 with A (note that currently I am with employer B).