Yes if you were otherwise required to file.

Yes you should bring previously filed and current tax documents.

Best to inquire with specific country embassy about visa requirements.

No there is no negative impact on the categories provided.

Yes you may include an updated I864 with current income.

Follow the advice of your counsel or contact USCIS directly.

Yes you should be able to do so without issue.

You can file a FOIA request for copy of approval.

No this shouldn’t be an issue for naturalization purposes.

Yes you may do so based on information provided.