It was discovered recently that the Japanese manual for Knuckles' Chaotix references functions for the sound test that require buttons on the six-button controller. Pressing X/Y in the final allows you to change the output (stereo/mono) or tempo, while in prototypes 0202-0210, pressing Z will enable a faster tempo (likely for the speed shoes), though this was removed in 0212.
Forum Link: https://forums.sonicretro.org/index.php?threads/adventures-with-chaotix.39934/
