I have written to Immigration with request to withdraw I-130 and I-864. I did not have official divorce decree at that time. Do you suggest I send it to Immigration? Or is that not my responsibility ?

Is there any way for me to check on the status of the pending I-751 ? How long does it usually take? I did not sign. What are the steps in the process for him ? If he gets denied then what happens ?

Thanks for all your responses and support.

If he gets denied... his green card is not longer valid regardless of the expiration date, and he will likely be placed into removal proceedings.

Should I provide Immigration with Official Divorce Papers ?

You may.. but if you don't send it along with the letter, it's probably not necessary.