I have a boxed set of Funko Inc. Wacky Wobblers of Kellogg's Snap, Crackle & Pop. They are old, but not that old cuz they have a bar code. Does Funko buy their own stuff back?

Not that I know of Funko HQ is mostly a new and more kid related pops for sale. You probably need to find a comic or collectibles shop for that or sell them online.

I saw ONLY new items for sale. Maybe at the corporate level? Don't know about the secondary market for Funko.

Offer up....

If by "buying back" you mean returning than most likely but I don't think you can sell them pop's from somewhere else

Maybe