Question [Q][Help] Porting android kitkat for a Jellybean device ??

Hi I am currently using a device with 4.1.2 on it and want to port kitkat to it ( READ ON )
Currently custom roms available for my devices are ports from other devices like huawei y300 and g510.
Recently a Slimkat version has been released for both those devices and i want to port it to my device.

My question is how do i go about it?? I found many guides about porting roms of same android version but dont know if cross version porting is possible.

Please Help