Is there any differences depending on the version that make the game faster or slower and why isn't there an IL leaderboard?

I believe the PAL version of the game runs a 50fps instead of 60, but from what I'm aware it doesn't effect the running speed of the game (though I could be wrong about that). As for ILs, this game isn't particularly active, so nobody's went out of their way to make one yet.

This is a game I'm particularly interested in. Has it ever been showcased at a marathon? I think if people saw it many would be eager to jump on a retro platformer like this.

A run was done at ESA Winter 2019 by Truljin (who I believe is now called NordESA). That's the only one I'm aware of.