I'm glad that you liked it. I played your game and saw that we do have similar concepts; I like it too. It really doesn't have Koyote Jump. I think it's just how the collision is set for the player. The reason why the player can fall into infinity is that I was going to add a death effect on when it happens. Like the camera will focus on a text above the level but sadly, I didn't have the time.
If you're still stuck at level 5, here's the walkthrough for the whole game: