Minors have the same rights as any other customer in regards to returning an item at a store.
We have never seen a store without a return policy, but of course its possible there is one. Whatever the store return policy is applies to you the same as to any one else of any age. In Arizona, there is no state law that requires stores to do any specific thing in regards to allowing customers to return items. This may be different in your state. You can try calling the Office of the Attorney General in your state and asking if there is a law about store return policies.