1. Jailbreak iPhone 3G iOS 4.1 using redsn0w 0.9.6 Beta.
2. Download Game Center for iOS 4.1 iPhone 3G archive and extract the zip file to your desktop (attached at bottom).
3. Launch Cydia on your jailbroken iPhone and install OpenSSH if you have not do so yet.
4. Connect your iPhone with your Computer and SSH into it by installing either CyberDuck for Mac or WinSCP for Windows.
5. Get your iPhone’s IP address from Settings –> WiFi –> ‘Name of your network provider’.
Here are the login details to SSH into your iPhone.
Server: IP address of your iPhone.
Hostname: IP address
Username & Password: Same as for Cyberduck.
After you SSH into your device, be sure to change the password from the default ‘alpine’ using the passwd command.
6. Now navigate to /Applications folder in your iPhone file system.
7. Copy the Game Center file you downloaded in Step 2 to this folder and set the permission to 775.
8. Choose which of the following functions you want to activate by selecting the corresponding folder in the downloaded zip file of Step 2. Note that the more number of features you want to turn on, the higher will be performance degradation.
Game Center + Multitasking
Game Center + Backgrounds
Game Center + Multitasking + Wallpaper
9. Now navigate to System/Library/CoreServices/SpringBoard.app/ and copy N82AP.plist file to your desktop.
10. Copy N82AP.plist file found in the Game Center zip file you downloaded in Step 2 and replace it with the
original N82AP.plist file of Step 9.
11. Now go to System/Libary/LaunchDeamons/ and copy the file com.apple.gamed.plist.
12. Go to usr/libexec/ to copy the file “gamed” (found in the downloaded zip file) and set the permissions to 755.
Restart your iPhone 3G and when you turn it back on you should be able to find Game Center on your Home Screen.