Two (2x2) passport style photos are needed.

Yes you should notify USCIS of the change of address between approval and oath scheduling.

Unclear why you would receive RFE after approval. Contact the VAWA unit by telephone for guidance.

You may petition your child in a foreign country.

Your sister would answer yes but her family would answer no.

Your question is unclear. Please rephrase and ask again.

Refer to the validity date for the visa.

You may file for a subsequent extension request within the time period of the initial request.

Yes you definitely can petition for your spouse despite other pending cases.

You may but processing times are delayed and you must establish clear eligibility for change of status.