Installing cyanogenmod 11 I have gionee gpad g3 whose specifications are 512 mb ram, 1.2 ghz quadcore processor and 4 gb internal memory. my device is not listed on CM supportable device list. so should i install it?
What do you mean 'should I install it?' What are you going to flash on your phone?

BTW since your tablet lacks official support, try looking on xda-dev if there's any unofficial support for your device. There's little to no hope so I wouldn't count on it much. Even if you can find an unofficial support, its likely to be very buggy and unstable. Better stick to your OEM firmware.