Came across this info on The Cutting Room Floor! @ https://tcrf.net/Moomin%27s_Tale

"Game Genie code 012-02F-E66 with the Japanese version will start the game in a debug menu similar to the one in Jankyuusei: Cosplay Paradise, where you can test music, sounds, view maps, start at any point in the game or return to the title screen.

While the code for displaying the debug menu remains in the European version, and can be activated using the Game Genie code 011-F1F-E66, the text was removed and so only a blank screen is shown."