L1 B Extension and COS process

[forumuser2018]

Hi Everyone,

 

I have a valid L1B visa till December 2018 and in progress of filing an extension. My I-94, PED and Visa end date are expiring on same date in Decemeber 2018.

My husband has his valid H1B till August 2019. 

Can someone advise on the following?

1) If i want to file for H4 COS before my I-94 expire in December 2018, by when should i start COS process.

2) If i opt to file for COS before Dec 2018, then from when would my period of authorized stay begins

 

Thanks in advance