H1B Visa: Can I File two petitions 1. extension 2. ammendment with extension with same employer two different clients

Hi All,

My visa/I94 ending by Aug 11, 2020.
I am working for a client A and the project ending in a month with client A.
I am trying to move to different project with client B with same empoyer.

Can i file two petitions as below

First one is extension with client A now ?
Second one as ammendment + extension with Client B once i completely moved there?

Ammendment + extension can I apply after Aug 11 or i should apply before Aug 11, 2020?

What happens if two petetions applied?
if we get RFE/rejection on first petition with client A after I moved to client B.

Thanking you in Advance