Cheat Mode (Strider 1):
Beat the game to unlock the "Player Set-Up" and "Stage Select" selections on the option menu. "Player Set-Up" allows you to select different costume colors, the number of energy bars, and the ability to permanently power up your Cipher.

Unlock Infinite Boost in Strider 2:
Beat the game with Strider Hien in Strider 2 to unlock Infinite Boost.

Unlock Stage 00:
Beat both Strider 1 and 2 to unlock Stage 00.

Unlock Strider Hien in Strider 2:
Beat the game one time to unlock Strider Hien.

Infinite Time:
Beat the game with Strider Hiruy. After you beat the game with Strider Hiryu go to Option Menu.

Thanks to Revolution reader Jason Sommerfield and Terry!