How to exit game in nintendo ds lite model usg-0100?

To exit a game on the Nintendo DS Lite (model USG-0100), simply press the power button located on the right side of the device. Hold the button until the system powers down. Alternatively, if you want to return to the main menu without turning off the device, you can press the "Home" button if the game supports it, and then select "Quit" or "Exit" from the menu options.