Press RUN at the title screen to come to the next screen. There you should press I, I, I, I, II, II, II, II, right, left, right, left, right, left, right, left. You now have 16 continues (instead of 2).
You will begin game play on the last level. Press Run, I. Select "Yes" (first option) then choose the last option. To select weapons, choose any of the other options.
First do the password code, then enter the following password. Format is Row #, Column #.