Employment Based Green Cards

I am looking for opportunities using the remainder option of my H-1B. I have a year and half remaining out of six years.

Now, most of the companies do not want to start the GC process immediately; they want to start after 6-12 months.
I have the following two questions:
1. What stage do I need to reach on my GC process when the remaining time on H-1B ends.
2. If my company doesn't want to start GC process immediately, can I begin this on my own using my personal fund?

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 ?

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).

Status of the H-4 EAD regulations

I am working for company A, last three years. In order to file green card I need to use my current experience(3 years) as I don't have previous experience to prove. Can I leave the current job from company A, go to another company(company B) and work for few months in ( company B) and go back to my previous company(company A) so I can use the three years experience for GC process? How long I have to be out of company A to use that three years experience?