Why i cant use some button with some game with usb controller? I bought a USB controller called 'ShanWan USB WirelassGamepad'. The controller claims to supports all the games but when I try to play 'Real Racing 3' and 'Fractal Combat X', I can use just the Analog Stick(or D Pad) but I cant use other buttons.  

I'm using Galaxy Note 2, Android 4.4.2 If it's relevant
Not all games have full gamepad support.  Manufacturers of these gamepads will claim that every game is supported which is only half true.  They will only have limited functionality.  I have the exact same issue on certain games using a G910 I purchased from geekbuying.

Here is a site that I use to check for full gamepad support.

Android Gamepad support