Can I take back two Firestick that are not in a box, but I have a receipt?

You should be able to return if they are within the return policy window which if i remember correctly is 30 days.

Yes, but you may have to pay a 15% restocking fee

I would say go ahead. Nothing beats a failure but a trial

I doubt it, if they are not in a box. Give it a shot.

It will probably depend on the reason for return of the item. However, they are very good about returns so you should be ok. Let us all know what happens.