Currently I am on F1 visa and today I got approved for H4. Meanwhile I also filed for STEM extension. Can I still stay on F1?

you may only have one status at a time. Did USCIS know you were applying for both?

Will I be able to file for green card if I get married with a US Citizens?

The answer is yes you can adjust status here. The rule you are referring to talks about students who have quit school, worked without...

Does my English fiance need a special visa to visit once we are married? We will live in UK but want to visit US/ 4 months year.

He can come and go on an ESTA after applying online (limit of 90 days in U.S.) but be prepared for questioning at the Port of Entry to show ties...

Correct I-94 Error

B-1 is fine -- it is usually shown as B-1/B-2

Can we work on EAD if visa is expired and I 485 is in process?

Yes if she has a valid EAD and AP through green card filing she can continue to work. Extensions are taking several months though so file...

How long will it take for an interview schedule when case transferred to NBC?

go to the USCIS Processing times link and then look up your District office to get an estimate only.

Your case would need to be thoroughly evaluated to determine if the I-360/I-485 is a good option. If there was a finding of a fraudulent marriage...

My L2 visa is expired but my EAD is valid until 4/19. Can I work for a US company without valid L2?

You and your spouse need to immediately leave the U.S. or file for a change of status to a nonimmigrant status prior to July 12 if I understand...

AVN

You may file your adjustment application when either Priority Date is current -- just make sure to correctly advise them which I-140 you want it...

Immigration benefits for spouses of veterans?

Honestly there is no expedite unless he is about to be deployed and even in that scenario under the current administration I would expect your case...