Ok guys, I found out how to unlock Ultra Core 3 and 4. Thx to RAH-66!
First you must install Bloody 4 Software ( IT MUST BE BLOODY4!!!), then switch between any Core Mode to another.
While switching the Core-Modes, unplug your Mouse when it is at ca. 25-30% on the Loading screen, like RAH-66 mentioned in his Guide.
For those people who mentioned that they're V7 mouse is not detected in Bloody 3 Software. When you first install Bloody 4 and unplug youre mouse while the Core is changing, the ID of the mouse will be transmitted to Bloody 3. Before you install Bloody 3 deinstall Bloody 4 Software! Then install Bloody 3 and plug in your A4Tech mouse. After that, you can activate the Core 3 with the Keygen and voila, it works!