Family Emergency - Drop box option

I have travelled to India due to emergency in family.
Could you please see if you can help me with the below.

My previous VISA got expired on 04/01/2020. My (only mine) extension approval(I-797) received couple of months back. But, My wife and daughter are still waiting for the finger print appointment. They received their receipt numbers in April 2020. But approval did not received as finger prints are not done.

  1. My family(Spouse and daughter) is still in US with extension receipt number (previous VISA expired on 04/01/2020). Are they still ok to stay in US with receipt number, even if i am not present in US currently?
  2. I am thinking to bring them in few weeks time. Are they eligible for Drop box option too?
  3. Any idea the earliest drobox option that we could get?
  4. if I don’t get any near slots for drop box/interview, what is the process for approaching emergency visa request.