Which visa category, regarding immigration is more fast? Fiance Visa Or spouse (wife) visa?

The K-1 fiancé visa is only available for US citizens sponsoring a fiancé, not green card holders unfortunately. So the spousal route would be...

Sent RFE response to partial address in the cover letter?

I would resend it. They won't mind if they receive a duplicate. Send using a trackable courier such as FedEx.

You are still in valid H-1B status and therefore your wife is still in valid H-4 status as well. It does not matter that your previous H-1B...

That's fine - you can apply for both. However, if your H-1B petition is selected in the lottery and approved, then you will only hold H-1B status...

No, you will only get 12 months OPT. You cannot reclaim the 12 months OPT you didn't use after finishing your Bachelors, unfortunately.

Can my fiance get a green card through marriage, US citizen marry visa holder?

Hello and thank you for submitting your question. I do not foresee any issues with your finance's green card application. You did not mention...

I filed I-751 in january 2017 as divorced. My second husband wants to file petition for me while I-751 is pending. Is it ok?

Yes, you can have your second husband file a new I-130 petition for you. No point in withdrawing the I-751 though. That is something you have to...

For EB3 visa adjustment of status require an applicant to maintain his/her status? I-601A currently applicable for EB3 ?

You could file an I-601A. EB3 is just like any immigrant petition.

There is no requirement that the job titles or even duties match. The PERM application is all about a prospective job offer - has nothing to do...

What additional documents do I need if applying for a change in status from an O-1 Visa to a B2 visitor's visa?

It doesn't make a difference what your current status is. The main thing is meeting the B-2 requirements.