I ordered a car part offline but it was the wrong part, could I return it at the local store. The part has not been used.

If from one of Walmarts vendors from on line, or with the app. Just go to the front center of the store, Customer Service.

Also it has to be Wal-Mart's brand and not another company.

Yes I also have made that mistake. And yes you can make returns to local Wal-mart stores.

Yes

Yes. Bring your receipt

Yes as long as you bring your receipt.