It would be nice if we had an & knuckles leaderboard(separating knuckles & knuckles, tails & knuckles and sonic & knuckles. :D

No

The best way to get a leaderboard added for those categories is to get people running them. We prefer not to add leaderboards for categories that will only have one or two runs on them.

ok

Sonic 3&K Co-Op would like to have a word with you Argick ;P Jokes aside, the only category that even changes from having &Knuckles is Knuckles himself, and it's only because of a timesave for a boss skip in Chem Plant 2, and MS2 boss skip. Other than that, the categories are identical as if there were soloing the level.