Change job with I-140 approved

[a_good_fella]

I have an approved I-140 (EB2 category) with priority date in August 2011 with my current employer. Based on that, my H1B has been extended till 2015. Please note that I completed my regular H1B quota of 6 years in November 2012. I fall under Scenario AC21 104(c).

I have 4 questions:
1. Can I change employment now? Is it safe?
2. Can I continue to have the same priority date when the prospective employer picks the green card processing?
3. How does my new employer pick the GC processing? What will I need from my current employer?
4. Does my new employer have to do the GC processing from scratch?

Any help will be greatly appreciated.

Thanks

[immihelp]

You can change job but your employer will have to start the greencard processing from scratch.