Do you only take returns on items bought in your store?

You can return the item in real packaging even you bought it online.

Got cash back on an item I purchased in store, don't know about online

You can return items bought in all stores as well as online items.

They will take online too

If you order on line and need to return the item, when you start the return it will tell you if you can return to store or if you need to send back to the company

In most cases Walmart will accept returns from any Walmart location.