Activate GameCenter on iPhone3G + GameDetection

You'll Need:

First you need jailbroken iphone 3G with 4.1 firmware (custom firmware if you depend on sim unlock like ultrasn0w)
OpenSSH - installed on your iphone from Cydia
WinSCP or Cyberduck (or every other SSH Browser)
And the Updated GameCenter Pack-v2
Mobile Substrate - installed on your iphone from Cydia (you may already have it if you use Ultrasn0w to unlock your phone)

Settings for Cyberduck & WindSCP

Make sure iTunes is completely closed

Cyberduck

* Server: The IP address of your iPhone. Settings –> WiFi –> “Your Network Name”
* Username: root
* Password: alpine
* Protocol: SFTP (SSH File Transfer Protocol)

WinSCP

* Hostname: The IP address of your iPhone. Setting –> WiFi –> “Your Network Name”
* User name: root
* Password: alpine
* Protocol: SCP

Getting Started

1. After connecting to your iPhone, Navigate to /private/var/stash/Applications and copy to this folder the Game Center~iphone.app folder.
After that, rightclick on the folder and set permissions to 0755 ( 755 ).

2. Navigate to /system/libary/CoreServices/SpringBoard.app/
Now you got the choose between different N82AP.plist 's. The plists are in separate folders which names describe what is activated in the plist.For example:

GC Only - enable only game center
Multitasking + GC - enable multitasking and gamecenter
Wallpaper + GC - enable wallpaper and gamecenter
Wallpaper + GC + Multi - enable wallpaper, gamecenter and multitasking

Choose the one you like from the downloaded folder and replace it with the one on the iPhone.

3. Navigate to System/Libary/LaunchDeamons/ directory then drag & drop com.apple.gamed.plist into the directory

4. Navigate to usr/libexec/ directory then drag & drop gamed file into the directory and set the permission to 0755 (755)

5. Go to /Library/MobileSubstrate/DynamicLibraries/ and copy PatchGC.plist and PatchGC.dylib files in this folder. Be sure that permissions set to 0644 (644)

6. Reboot your device, and youre done.