yes. 10 mhz games will work with 12mhz oscilators. framerate is not tied to clock speed. you may experience lack of slowdown in situations where slowdown would be, but unless you have 1'ccd the game multiple times you will never notice. same goes for 12mhz games with a 10 mhz crystal oscilator. they will work but there may be a slowdown discrepancy, however it is negligable. unless you have spent countless hours playing the game and know it like the back of your hand you will not notice.
all i know is that 10mhz games will work with a 12mhz crystal and vice versa. idk if the a board has to be dash or not for it to work. maybe someone ewith more experience in that can give that answer. i personally have used a mercs board with a 12mhz crystal and have played it for hours and hours. i also know there are people who are using an a board with a 10mhz crystal for their multiz and have sucess doing so. it may be something to do with your C board? if you have the proper b and c board i dont see why it wouldnt work if it works with the multi.