According to some section under some law relating to copyright holders, game companies, and Trade Marked products by producers, it is a very strict policy not to use anything from one game to the other without expressed permission from the copyright holders, seeing as you do not own it.
"BUT I DO! I BOUGHT IT!"
No, you payed for a lease of private use.
"BUT THE ADVERT SAID 'OWN
Then sue them for false advertisement! No form of any of its contents should be given out free because it would be thought of as giving away the whole game for free. This law is SOOO strict that you can find every piece of every game in every other game, short film/animation, or feature length. Collect them all, and you've been able to turn your Demo into the complete game.
This kind of debate/war has been through Massassi among other forums with mangles, sabers, bazookas and phantom swords. Why should it stop now?
(get law books ready to catch all loopholes)