You should not be dealing with all of this. If it's returned to you as undeliverable, just refund the buyer minus any non-refundable fees like the shipping costs and your final value fees, and move on. The buyer is responsible for getting their address right the first time.
The buyer cannot change the address on the order after they have paid, so that part is just a misunderstanding on your part about how this works, but you're really going way too far with this. Refund and move on. If you don't wish to block them, they can then repurchase the item with the correct address if you relist it.
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