Press LS, RS(2), LS, RS, LS(9), RS, LS(6), RS, LS(4), RS at the options screen (with Gir Draxon's face displayed). Gir Draxon's eyes will glow red and the word "Cheater" will appear to confirm correct code entry. The Boss will appear after the first wave of enemies is destroyed. During the game, pressing LS will restore shields, holding LS will make the Raven invincible, and RS will stop enemies.
Hold LS or RS to keep the Raven at whatever speed is set with Up and Down (even in reverse). The Raven will stop when it runs into an object.
Destroy the lower-left obstacle (seven o'clock position on radar) on level 1 to advance three levels. This will require multiple shots, and works even with the difficulty on "Practice." Shoot at a similar obstacle at the same location at this new level to advance to the end level.