Can a store refuse to take an unused item back with a reciept?

No they should definitely take it back if not then contact Cooperate.

Depends on the store return policy. Often there may be a time limit but there are stores that don't accept returns. You'd have to check. Maybe contact the corporate office.

Yes they should cause its unused and you have the receipt

They shouldn't be able to as far as I Know. Take it to another store if possible