After i obtain a immigrant visa can i use it to obtain o job meanwhile im waiting for my greencard

At a minimum you have to weait to obtain work authorization

Can i get a green card by marrying a US citizen?

As long as you entered the US lawfully your US citizen wife can sponsor you for a green card. You will have to provide evidence that the marriage...

If I want to study in university may I enter with o1 visa and changed it to student after one year?

You may be able to study as long as you are also workingpursuant to the temrs of your O visa.

it most likely will not effect your immigration status.

Can i be deported if i have only one felony of pocession of512lbs of mariguana?

We would need additional information. You need to consult with an attorney as a matter of urgency.

How does Divorce affect our residency?

If your permanent residency is unconditional divorce will not affect your status

How can I withdraw an application for Employment authorization?

I agree with my colleague

I would immediately disclose it and revise the 485 to show employment.

I came to this country as a baby from Ghana on my mothers visa with my other two brothers on the same visa and passport.

I agree with my colleague

You can try but most likely you will need the I485 approved first.