L2 to H4 COS delayed

[itsmeamik]

This is my situation:

I am the principal applicant in L1-A, living with my wife and kids in US (in L-2). I-94 end date was 10/Dec/2019.
My H-1B petition got approved along with Change of Status (COS) on 25/Nov/2019. New I-94 is extended till Apr 2021. 
Visa is not stamped yet.

H-4 COS (L-2 to H-4) for my Spouse and kids was not filed along with my H-1B COS but filed separately on 5/Dec/2019 (L-2 I-94 was still valid by this date).

I would like to know: 
A). If there is there any serious implication because of the 10 days delay in filing H-4 COS?
B). Is there any duration limit till which my family can stay in US? (or) Can they continue to stay in US till H-4 gets approved?

Thanks.

[ArunAM]

Hi itsmeamik

I have a similar situation, how long did it take for the L2 to H4 COS to arrive after you filed it with USCIS