Currently Zing has a few items up for a Buy 2 Get 1 Free sale. I was wondering if it's allowed by the store to purchase your items, and then later on trade one for an item that is NOT on the Buy 2 Get 1 Free sale. Or do you think they would make you purchase off the sale list/return your free item?
My example:
There are three Harry Potter pop vinyls that have part of the Hogwarts train. Each item is $55.02. However only two of them are on sale. Do you think I could buy two of the Ron pop vinyls and 1 of the Hermiones (thus getting the sale), and then later return one of the Ron pop vinyls for the Harry one?
I have no experience with Zing, but from my experience working in retail I would expect the same: we would always process the return/swap so that the customer would be getting exactly the deal/discount that they should logically be getting for their final purchase. Sometimes the auto-discounts in the computer system would get annoying for that so the simplest thing to do is the return the whole purchase and put through the whole new purchase.
My expectation would be no, your idea would not work. If you go to return one of your original 3, this would void your "buy 2 get 1" deal, as you have now only bought two. This would mean you'd be paying full price for your Harry and giving your Ron back for no gain.
However, if the way that they process the discount is to take 33% off each figurine, rather than making the third one $0, AND the sale and refund is processed by either a computer or a staff member that doesn't care - you may get lucky and just need to pay the difference for the Harry (so you end up with a full price Harry, and a 66.6% price Hermione and Ron. The chance that they would let you swap a 'free' Ron for a 'free' Harry is extremely low.