Can I apply for F1 visa after applying for visitor visa extension?

Yes you can apply to change your status.

I was hired by a company 5 weeks ago. Let go this week, I asked why, answer, cannot say. If I ask why shouldn't they tell me.

This is an employment law question. The contract that you signed for your employer would be a good place to start looking for answers.

This is not uncommon from the investigative unit of the USCIS. You should be getting an answer soon.

I'm naturalized making petition 4 parents, How much income do I have 2 show. household (1) just me

You will need to compare your income with the poverty guidelines (USCIS form I-864P).

I am on H4. My sister is a citizen. Can she apply for a green card for me? How long would it take?

Your sister can "petition for you" under the fourth preference; however, that may take longer than the EB3 wait.

I-751 interview with IO.

I agree with my colleague.

My colleagues are correct.

Can a green card holder who is also a Canadian Citizen, be stopped from entering to us for having Canadian criminal records?

Maybe, depending on the criminal conviction.

Selected as the best answer

Can a I94 visa lead to a green Card?

I suggest that you meet with an experienced immigration attorney. An I-94 is not a visa.

My brother file a I130 since 2003, and it has been approved

It depends. What is the country of chargeability? What is your country of origin? Where are you residing?