To get Free Play, on the title screen when the word "Press Start Button" flashes, hold L1,L2,R1,R2 and press Start. Continue to hold the top buttons and press Up 7 times, Down 1 time, and Up 4 times. The cursor should highlight Option. Now press Start on Option. Go to configuration and turn off Credit Limit to get Free Play.

First, you have to beat the game in Arcade mode. Afterwards, go to options and you will find, under configuration, Number of ships set to 13 and a 13 ship order thing near the bottom. You can choose this and be in a prototype ship. It has no hyper laser attack and no special attack but it's fun to try out. You have to be careful though because once you die, you lose the ship.