H1B Amendment/Extension with Client B while H1 Extension is pending with Client A

[chaitanya1015]

Hi,

Can anyone please shed some light on the below scenario:

I am currently working with Client A and my employer has filed a petition for H1B extension. Meanwhile I got an offer with Client B.

1. Is it permitted to do an Amendment + Extension with Client B while Extension with Client A is already in progress?

2. If permitted 
Suppose, if my current H1B extension petition with Client A gets denied, How long can I stay legally on my Amendment + Extension receipt notice with Client B as my i94 got expired on 4/7/19?
Is it permitted to move to Client B if my extension with Client A gets denied and Amendment + Extension gets approved with Client B? Say for example if my H1B Extension with Client A gets denied on April 20 and my Amendment + Extension with Client B got approved on Apr 29 assuming premium processing is done. So what will be my status for those 9 days?

Thanks in advance for your time and clarifications.