US Immigration from Nigeria

Hi guys, can a person with an extension letter of 4 years after filing for I-751 apply to join military reserve?

We have been waiting 3 years since initial application materials were sent. We were documentarily approved Dec 2022. Our status shows "At NVC". Does that mean it left NVC Dec 2022? Please, help.

I read the tip in the K1 Fiance Visa Guide where it gives a tip regarding Vaccination Records that says:

"The K-1/2 beneficiary will be required by the embassy to have a "medical" done prior to the visa interview. Part of this interview will require that previous vaccinations are documented and potentially additional required vaccinations performed. Once this is complete the doctor will note this on a DS-3025 form that will be sent to the embassy. During the medical appointment request an official copy of the vaccination records from the physician (or a copy of the completed DS-3025 if they will give it to you) as this will be helpful to have on hand in the future (specifically it can be helpful when filing for Adjustment of Status if your DS-3025 form is not available)."

However, I forgot to send that to my Fiancee before the Medical Exam and vaccinations which took place yesterday. Therefore, there we have no paper copy. Does anyone know if this will definitely cause a problem when it comes to filing for Adjustment of Status, or do they possibly have some sort of electronic copy they store somewhere in the system?

I was scheduled for interview in July, but my wife couldn't find our marriage certificate(still searching for it though), can I go with a scanned copy? Hope it's acceptable? I need urgent responses to this. US-Embassy in Lagos, Nigeria.

What are the procedures of fianc visa processing?