here you are guys how to go through the demo in hard mode
"To enable hard go to your gamer profile in the dashboard and then change your default game settings. Go to general, then change your difficulty to hard.
Start up the Bioshock Demo.
Hard should be highlighted when you have the option to select your difficulty. Make sure not to move the cursor or you will not be able to select hard again unless you hit B and then return.
Hit A."
"To enable hard go to your gamer profile in the dashboard and then change your default game settings. Go to general, then change your difficulty to hard.
Start up the Bioshock Demo.
Hard should be highlighted when you have the option to select your difficulty. Make sure not to move the cursor or you will not be able to select hard again unless you hit B and then return.
Hit A."