Yes, they can look up any purchases made on your membership.
Yes, you can return with out receipt as long as you have active member ship.
Yes, it is connected to your costco membership card.
Yes you can they have it on their data
Yes, under your membership account even if was years ago.
Even months after the purchase date as long as your membership did not expired
Yes they look it up under your membership.
Yes you can
Yes
Yes, with membership details and only the purchasing membership(membership # has to match) can return.
Thanks! Your answer is awaiting moderation.