I've been downloading roms for a couple of months from this site but always been to shy to post! If someone could answer my questions that would be great

1) Does it make any difference if you open the b door and change the amount you've paid in? Will it think I've paid in more than I have? Or will it not change it at all?
2) If a rom is made for an earlier version on MFME will it play the same on MFME version 10.1?
Thanks x