No Best Buy will not, they barely support their own purchases buy elsewhere.
If unopened, I'd expect it could be treated as a gift for store credit. Without receipt, they cannot credit your card and you wouldn't get cash unless you could prove you paid cash originally.
Probably store credit unless you have a debit or credit card printout of transaction. They will be able to look at their log of sales and verify the sale. It is strange to return a movie if you opened the package or if the CD didn't play correctly.
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