L2 COS and EAD Concurrently


I am currently on H-1B and my spouse is on L1A. I want to file COS to L2 based on my spouse L1A and concurrently also file EAD application.
Now what i understand is that i-539 (for COS) and i-785 (for EAD) can be applied concurrently. I am currently a resident of Wisconsin State. My questions are:

1. Where do I mail both the application (i539 and i785). As the address mentioned on USCIS website on "where to file" section is different for both the applications. And I was not able to find anywhere on USCIS about information on where to file when filling concurrently COS L2 and EAD.
2. Do I also need to pay for Bio-metric fee?
3. I had EAD based on my spouse L1B a few years back. Since then my spouse moved to L1A and I move to H1B and the previous EAD got expired a few years back. So do I now file my i785 application under "renewal" or "fresh" EAD.
4.. What happens to my H-1B once i change my status. Can i still utilize same petition in future to move back to H-1B in case i get an employer ready to the movement.

Thanks in advance for your advice and help.