@ChristiJunior Another world? Do you mean the "Dark Side"? I already have unlocked that. I tried it, but it seems to be a gauntlet with no health refills and I only barely made it to the second boss. I decided to leave that be until I do the rest in hopes of getting better at the game.
BTW, I thought the rabbits were kind of lame; but the RoboBrood was the best boss in the game. And it had awesome boss music too.
Yes, I am. Some times I jump to my death thinking there was a floor in front of me but I was just not perceiving 3D on a 2D plane.

Other times the camera is the biggest enemy. Thanks!

I noticed that I did get better than I was when I started. I tried some of the early scarecrow timer challenges that took me tens of tries and now I can do them in one go, for some reason.
I don't know if 100%, since some times I'm standing on the map where the clue says a moon is supposed to be, but I can't find any; but I'll try. After that, I'll move on to Mario 3D Lazy Collection and start with SM64.
That's like two polar opposites. lol