-To add seven more lives, replace the last three characters of any working password with "CBS".
-To get an extra life in Snow Fortress, after destroying the electrical cables the tank on the lower left of the screen above the building has a free life inside it.
-To gain around five lives in River Raid, stay in the helicopter before you get the F117-A. Go to the very top right corner of the level. Destroy the twin guns and blast open the little pyramids to gain around five lives.