Why USCIS, after informed me that it approved and sent to NVC, transferred my petition to Virginia USCIS office?

It may be best to contact USCIS to determine why your case was transferred as there may be various reasons for this, including case volume at center.

The certificate should be valid if it was issued by an appropriate government authority.

How many times will you apply for a re entry?

It is not advisable to continuously apply for a re-entry permit as your intent to permanent reside in the US could be questioned.

Petitioning a step daughter ?

Yes you may assuming marriage occurred prior to her turning 18.

Can a joint sponsor use his spouse's income as well?

Yes you may but the spouse would need to file I864A.

That is not advisable and can present issues when naturalizing.

Immigration- i`m Married with US citizen and I-130 approved ?

You may adjust your status based on your wife’s status. Best to consult with an attorney for guidance.

No she will need to reopen the proceedings in court, then file the I485 in court.

Travel time for N-400?

Yes immigration will use the I94 information to verify your entries and exits from the country.

Do I need to have copies of my original forms and documents when I have interview, example, I485, I765, and I131 etc....

You should have copies of all submitted forms and originals of most biographic documents.