Black Shades Cheats Problem?

[Mystical Mayhem]

I open up the config, and I see these things: Screenwidth, Screenheight, Mouse sensitivity, Show FPS and other info, VBL sync, Blood, Blur, Main menu, Custom levels, Music, azerty keyboard, and invert mouse. I don't see developer option anywhere. And when I try to change one of the options, it says "Access is denied".
EDIT: I found a way to save it. But I need help on the problem where Developer option doesn't show up in the Config.txt file. I try and see if it's Custom levels option, but when I save it and open the game, it lags my computer like crazy and I have to restart my computer. I have no idea why it lags, because I've tried level editors on other games (Even for the PC version of Trials Evolution.) and they run fine. It shouldn't lag, even for a early 2000's game running on a less than a year old computer. Did I download a faulty game? Or did it download fine, but I am just doing something wrong?

[melchips]

For the first problem, I guess you have to check the file access rights for your user (as you don't mention which operating system is concerned, I can't help you). Obviously, you have to enable write access to the file.

For the developer mode, if I can recall correctly, the developer option is activated by setting the "Show FPS and other info" to "1".
"Custom levels" is not related to cheats, and will parse the file "Data/customlevels.txt" to set the levels.