Switching jobs with H-1B (and H4) extension in progress

[Videsha]

Dear all,

Thank s in advance for your inputs.

My current H-1B petition (and visa, including that of H4) is valid till Apr-1-2022.
Extension application (I-539) has been filed by my current employer (Company A) for both H-1B & H4 visa.

Now I'm getting an offer from Company B and, should I go forward with switching jobs, Company B would only sponsor for H-1B and H4 processing is on my own..

Can Extension application (I-539) be withdrawn by Company A for both H-1B & H4 visa once I drop paper?

Please tell me with, 2+ months left in my current visa, is it possible for Company B (and myself) to file a new Extension application (I-539)? Is it needed?

Regards,
Videsha.