When Sonic 3B was developed, the levels were not meant for Tails. Still many places were fixed before the release of S&K because the lock-on with Sonic 3 had Tails as a playable character. The evil Knuckles' demos are always placable objects on a level even though the bosses are not, and both are kind of like demos that needs to be located at perfect places to not mess up any other graphics or palettes. Knuckles at Lava Reef Zone Act 2 bounches a stone at Sonic & Tails so that they will fall down into the pit, and by that demo also load Lava Reef Zone Act 3 which is the boss level. Knuckles' path comes out from above the demo and all gates are closed by hard stones only breakable by Knuckles himself. This is to prevent Tails (and possible Sonic flying with him) to get into Knuckles' path and by that go backwards through the Zone and collect more rings and power-ups.
Knuckles' demos have usually hidden blocks that prevent Sonic and Tails from comming too close to Knuckles during the demos. Now these blocks are not to be found in LRZ2.
Bug 0003 description:
Tails can land on the little area where Knuckles' path joins Sonic's. By that Tails can fly over Knuckles's demo without trigger it. This will make Tails able to get an extra life, but also see some unfinished block mappings layout before dying.
Bug 0003 was never fixed!
The video of the bug (taken from the last version of Sonic 3 & Knuckles ever compiled) can be downloaded here:
More bugs/bug-fixes will be posted later. Post your comments!