On H1 and move to EAD


I have been with my current employer for more than 10 years. I am currently working on H1B (EB2) and my employer had applied for my GC. I am still waiting on AOS and my PD is Oct 2009.

I got my first EAD/AP almost 5 years back but always worked on H1. Now I am thinking of moving to a different employer on EAD. It is a big decision for me and need your expert opinions regarding this.

1. I am getting confused with AC21 and EAD? They are different but I do not see anywhere (forums) that says if NOT using AC21 AND directly start using EAD..... these are the list of possible things to keep in mind.
2. While working on EAD, should the Job title, description and wages be the same when my current employer applied for my 485/GC?
3. If my H1 still has another valid 3 months and I decide to move on EAD, what happens to my H1?
4. Can I switch to a new employer on W2 Contract? That is, I am not a permanent employee of the new employer.
5. Do I have to notify my current employer of the move?
6. Do I have to notify USCIS of the move?
7. Can my current employer revoke my pending/approved applications (if any)?
8. Can I go back to my original employer back on EAD?
9. Should my new employer fill out additional forms so that my GC application is still valid? What paper work should my new employer be doing?
10. What happens when I get my GC? Can I move to a different employer with my GC?