The way I see it...
- As far as stages go, most classic games follow a World 1-1 or Stage 1-1 formula. Even though it's very similar to a Sonic game, I wouldn't worry all that much about splitting stages up into seperate parts so to speak.
- Maybe for the end of the stage, you could have a checkered flag or something. Not quite sure.
- Again with the act thing, you could have a title card. Mainly to indentify the location of where the player is, or maybe have a map and not have a title card at all.
Even so, this is still the most original game I've seen.