Ninja Gaiden 2: The Dark Sword of Chaos / Ninja Ryukenden 2

Codes, passwords, hints and secrets for game Ninja Gaiden 2: The Dark Sword of Chaos (Ninja Ryukenden 2: Ankoku no Jashin Ken (忍者龍剣伝 II 暗黒の邪神剣), Shadow Warriors 2: The Dark Sword of Chaos)

Sound tests

Hold Up/Left + Select + A + B and press Start at the title screen to display Ryu and allow all music from the game to be played.
Alternatively, press Start after the title screen fades to display it again. Press Up/Left + A + B +Start to display Irene Lew and allow all music from the game to be played.
Finally, press Start after the title screen fades to display it again. Allow the screen to fade again and press Start. Press Up/Left + A + B +Start to display Ryu and Irene Lew and allow all music from the game to be played with a volume and song title display.

Unlimited lives

Begin game play on level 4-2. Jump up and intentionally get hit by an opponent to land on the first ledge of the screen. Collect the extra life, return to the ladder, and climb up to the screen where your character was hit. Repeat this process to collect as many lives as needed.