I am new to speedrunning and interested to run this game. I own the game on 3DS but noticed the platform seems not to be present in leaderboards even if allowed. Why is that?

probably just harder to record a run, as that's required

the 3ds virtual console version is acctually the slowest version. i think it saves slower but that might be wrong

I actually heard emulators are the slowest, but I'm new to this so I don't really know

wii u is fastest, gba/emu is second and 3ds is slowest. For beginners or in general i wouldnt say that that timeloss matter. As you can see the wr is set on emulator which is 30 seconds slower then the wii u. If you have a 3ds capture card and the game for vc then i'd say run on that. But if you have a wii u or a pc for an emulator you can run on them if you want to save those extra seconds.