100% means completing everything that is tracked by the game and/or gives you an award, not doing everything. You don't do Green Hill in Sonic Adventure 2 as part of the 100% run because it doesn't give you anything, only thing that's relevant to progression is getting all 180 Emblems. Similarly in a more casual sense, you wouldn't consider walking into every single building in an open-world game like GTA or Spider-Man to be required for completion...
How? Again, the layout isn't different at all nor is there anything locked behind doing them.
Why is it necessary according to the rules to do duplicate races at Night? There is no unlock or bonus related to doing that, it's only a visual change within the race itself.
nope this game is way too obscure I discovered it a couple weeks ago when browsing random roms LMFAO
the emu option exists on the leaderboard
It's a very significantly different game, you don't need to look at it in detail to see enough difference for there to be a big advantage in some areas.