Figure Fighter VS/Unused

Rhythm Heaven Megamix
Figure Fighter VS consists of the following versions in Rhythm Heaven Megamix: Note that despite being based on Figure Fighter, Figure Fighter VS is internally stored as a separate game.

Unused Content
In Figure Fighter in Rhythm Heaven Fever, punching the sandbag was accompanied by a red hit spark. In Figure Fighter in Rhythm Heaven Megamix, this hitspark is larger and has an orange inner section. Neither hitspark sprite is used in Figure Fighter VS, though they remain in the game's textures anyway.

There is an unused sprite of the Muscle Doll's eyes displaying a red color, leftover from Figure Fighter in Rhythm Heaven Fever. In Rhythm Heaven Fever Cast, the doll's eyes flash red as it bobs to the music, but this detail is never seen during the actual game.

The sprite sheet for the red Muscle Doll has a solid color platform-like sprite and a small "+" symbol, which go unused. These sprites do not exist in the blue Muscle Doll's sheet.

Regional Differences
There is a sprite in cellanim/muscleDuel's "Button" assets, showing a stylus tapping on the screen with the message かんたんタッチ (Kanta n Tatchi) next to it, shown in Simple Tap mode on the bottom-right of the touch screen. While this is used in Rhythm Tengoku: The Best+, the icon and text are taken from other sources and the message is shown on the bottom-left side in the international versions of the game.

Miscellaneous
The Debug Menu for Rhythm Heaven Megamix lists a game called Darts (ダーツ) right before Figure Fighter VS. The textures for this game include a dartboard and a copy of the sprite sheet from Sneaky Spirits 2 (though oddly the tree's sprites and animations match the positions of the fountain in Sneaky Spirits instead), suggesting it would be a game based on shooting arrows into the dartboard in some way.

The text for the Badges given for winning a specific amount of times in Figure Fighter VS internally uses the name "Darts", suggesting this game would've been playable in StreetPass Terrace instead of/alongside Figure Fighter VS. These names also show that the player would've originally received them for winning 1, 5 and 10 times and against all characters, while the final game rewards the player for winning 1, 10 and 50 times and against all 15 opponents.

Interestingly, the Official Game Trailer for Rhythm Sesang: The Best+ uses the Japanese voices for Figure Fighter VS. While this is available as an option, the trailer does not make mention of it.