Am I still eligible for a refund on eBay if the seller puts no returns accepted and says all sales are final?

if its counterfiet just email ebay they will get you your money back no matter what.. they will attempt to contact the seller.. do research and they will give your money back just takes about two days or so

You open a claim with eBay for 'item not as described' and see what eBay says. 'All sales final' disclaimers do not apply to misrepresented items.

Your taxes would not be affected

If it was advertised as real and is not, then seller has committed fraud, which is a crime.

yes, file a complaint with ebay