What happens after the ninth stage. The table at 0x4E1B has ten pointers and the tenth repeats the first, and 0x7545 restores thirteen initial values —the stage and its mask among them—, but it has not been followed in the emulator.
The script at 0x53E4 that starts each life, with its timer at 0xE24D: how it is walked is known, not what each byte says.
Types 0x93/0x94 —the blue figures on the trunk— and 0xC9/0xCA: which piece they draw is known, not what they are in the game.
The scoreboard's metres. The height is divided by sixteen (0x66C5), but how many steps make a metre has not been measured.