EAD/485/140 + new Job

[H1B_140]

Hi,

Questions:
1. my EAD is getting expire in the month of may 2005, what would be good time to file for extension?

2. Before apply for EAD extension, can I apply for another job? is it safe?

3. what is the procedure if I change the job and then apply for EAD extension?

4. my 140 is approved and 485 will have 6 months in next 4 days , is it safe to change the job after a month or so?

5. I heard that if I change my job then I will have REF in my 485, is that true?

6. what would I need to do to change a job? I mean what document(s) I will need when I go for another job.

7. will there be any difference in the processing and application in the job, if is:
a. permenant
b. consultancy

8. What new employer will need to do to take over my processing?

9. what is AC21?

I know too many questions but be on safe side and it might help others too.

Thanks