So you've downloaded the Crackdown 2 demo.  You've been playing it and trying to unlock Achievements but not sure how to unlock some of them.  Or maybe you are disappointed at being only able to play for 30 minutes.  Well thanks to the magic of the interwebs both problems have a solution.  Shown below are two videos.  The first shows how to "pre-unlock" 100 Gamerscore points for Crackdown 2 when it comes out and the second video shows how to get unlimited time to play around in Pacific City.

Good luck and enjoy Agent.

 [UPDATE] Fixed total Gamerscore.  It's actually 100 not 200.