How do you buy diablo -back to hellfire?

you can buy him on e bay or at myer,Kmart,safeway or trade with some guy.

You can not.

They purchase your old technology back, so you can buy something new.

http://www.sealifegifts.net/DEVIL-FISH-826.html

Probably not, the U.S. is one of the most powerful and successful countries in the world. So no, a specific group of people cannot buy the country