Yes you can unlock extra perks on Call of Duty four but you have to be playing on live and gain ranks. to do this you must win round with 1 or more kills.
There are no cheats for Call of Duty 4
you can find a list of achievements at: http://www.xbox360achievements.org/game/call-of-duty-modern-warfare-2/achievements/ and also a guide for them at:http://www.xbox360achievements.org/game/call-of-duty-modern-warfare-2/guide/
You can't earn achievements while your using it in the SAME playtrough. Restart the missions without the cheats enabled and you'll be able to earn the achievements again.?I would recommend you finish the campaign first (on veteran if possible) before enabling the cheat codes
They do nothing besides earn achievements.
complete challenge "silent veteran II"
Easy, Normal, Hardened, Veteran
a weird box with night vision gogles
get 50 silenced weapon kills after you prestige
Nothing happens other than getting the achievements and trophies in modern warfare 2. But in modern warfare 1, you get to unlock certain cheat codes that can be used during the game.
get the trip activated c4 its in your perks if you've unlocked it
you have to get all of the Intel and complete all of the missions on veteran
play all the campaing levels on veteran and beat them
The Call of Duty 4 Achievements for Xbox 360 can be found here: http://www.xbox360achievements.org/game/call-of-duty-4-modern-warfare/achievements/