How should we send EB1 ( I140) ?

Suggest you send the I140 with the supporting evidence by paper filing.

Online Marriage and F2 visa

Generally for a marriage to be considered valid it must be valid where the marriage occurs and under the state jurisdiction within the United States.

I am J1 visa holder and working as researcher. I came to India for family emergency and now due to lockdown I stuck in India.

Your visa should remain valid particularly under the circumstances regarding travel.

Consider filing using a paper filing and consider including your evidence with the filing.

Yes E2 is permitted under the immigration rules to be a registered agent.

Can an offender with life in prison who is not an american citizen nor legal resident request his deportation?

It may be possible he should speak to his attorney.

There is no appeal for an adjustment of status denial. If you remain eligible you should refill.

If you do not answer the RFE to satisfaction of USCIS it is likely to be denied. If you provide satisfactory evidence it will likely be approved.

Yes - employment is good evidence although it may not be sufficient on it’s own. Recommend you have additional evidence. Physical presence and...

Did my employer send the H1B petition to right USCIS service center?

You can check the USCIS website. However USCIS changes processing centers regularly