The final four levels just aren't as creative as the first four, and the music isn't as good, either. I have beaten the SMS version. I may have beaten the Turbo version but I can't recall. I bet I could beat it with a Game Genie... if one existed.
I am really sad that the bonus stage that's in the SMS version is missing from all other versions. That was a really cool level and had some great music. I'd definitely add it to the list of desirable levels.