If you don't have a receipt, try to make the return within 30 days and the company may be able to find your purchase in its system if you used a debit or credit card for the transaction. You'll need to show ID to return items without a receipt.
Venom Snake is the doppelganger that Solid Snake killed in Outer Haven believing he had killed Big Boss. However Venom Snake is the main character in Phantom Pain (I think it's explained at the beginning of the game).
Input validation, also known as data validation, is the proper testing of any input supplied by a user or application. Input validation prevents improperly formed data from entering an information system.