That is an answer for @Kujako and anyone who doesnt have a original unmodified C Board. We strongly recommend to use unmodified C Board from the type indicated in the instructions.
Each game uses a different B-XX chip on the C Board. The B-21 can be reprogrammed using the method that ArcadeHacker explained, so that they will behave like any other B-XX chip.
In order to have the B-21 programmed you need access to the pins that I specified above. Check the github for more info. If you are not able to program the B21 as something else, you wont be able to play any other game.
Each game uses a different B-XX chip on the C Board. The B-21 can be reprogrammed using the method that ArcadeHacker explained, so that they will behave like any other B-XX chip.
In order to have the B-21 programmed you need access to the pins that I specified above. Check the github for more info. If you are not able to program the B21 as something else, you wont be able to play any other game.