Some Megadrive games has a lockout code built into them, is to possible to by pass this lockout code by modding the PCB of the cart at all???
probably not, and its not necesary. most all sega cart systems are easy enough to mod imports and there are also a slew of MD/Gen import adapters available, some that bypass internal lockouts. The best way however is to get a Game Genies and use the import codes written to play just about any game on any Genesis/MD.