Theres one easy way to defeat all of the stage bosses.
1) On the first boss all you need is a pod. Wait until he moves his tail, then shoot your pod into the middle to hit him. Repeat until he is dead.
2) For the second boss you'll also need a pod. When you come into the boss screen, try to fire your pod next to the opening at the top without overshooting. Go to the bottom lefthand side, get low to the ground and as close as you can to the plant. Now call your pod back to you and it should be stuck in the bosses hole. Stay where you are and the boss should never touch you. It will look like your not hurting him, but give it a chance and he will eventually die.
To unlock the De Souza drawing editor, you must finish the color-enhanced versions of R-Type I and R-type II as well as R-Type DX. Then, at the main menu, push the d-pad RIGHT - the De Souza drawing editor option should appear!
While playing a game, hold B and power the Game Boy off and on while continuing to hold the button. The game will resume at the start of the last level played with five lives but no points or power-ups.
To skip a level you've already completed, pause the game then press B.
To annihiate nearly every enemy on the screen, you must be playing R-Type II and have the largest pod attached to your ship. Charge your beam meter and, prior to unleashing the mega-blast, deploy your pod. Now release the fire button and begin tapping it rapidly!
(Note: The cheat has no effect on end boss.)
For invincibility, complete R-Type DX using no more than 10 credits. Then, during a non-DX game, press Select + A.