If your status is set to expire apply for an extension.

Yes employment is permitted with the EAD. The L2 approval will come but is not necessary for employment.

How can I help a friend get a visa or green card through sponsorship or other means?

You may provide the financial support necessary for her to obtain student status F1 in her own right. Other than that there is little but you can do.

Is international travel to the US from Russia permitted on a valid immigrant visa in current COVID-19 situation?

If the immigrant visa was issued before the travel ban should be able to travel to United States.

While it may be possible to change to a J-1 Au pair it is probably not a feasible option. Better to remain in school finish your studies and then...

-When NVC notifies that visa case has been opened based on I-130 approval, does it mean a visa is expected to be available soon?

The visa cannot be granted until the priority date is current.

When i get H1B approval from USCIS, is there a particular time period within which i should exit the US and get stamping?

The H1B status assuming you applied for a change of status allows you to remain in the United States for the time of the H1B approval. You do not...

What is Legal status after receiving all receipt notices for adjustment of Status from USCIS?

Yes she is lawfully permitted to remain in the United States pending a decision. She also has permission to go to work they obtain a Social...

Do I need to file Supplement J for the final decision on I-485 (interviewed in Oct 2019)?

You need to wait for your priority date to become current. If supplement J is needed they will let you know.

Since it has been closed administratively you need to have the case opened and acted upon. There is normally a basis for closing administratively...