Ohey, this is pretty good! I love this kind of hacks, and I wanted to give it a shoot as soon as I saw it.
The design is more or less good: I liked how you added the possibility to double-jump in some levels and how you made levels clearable (that is, by collecting reskinned yoshi coins). It's pretty unique, although you could've done much more with just these two gimmicks, but I don't complain much. Maybe, the only complain I'd make is the fact that some sections have blind jumps: you could YOLO most of the times since you'll have the double jump, but it's still a negative aspect. A coin trail to help the player would've been great.
Aesthetics, aw geez I loved them. The original character, graphics, everything aesthetically-wise is pretty appealing to me. Nothing much to say here, except that sometimes, the BG is confusing. An example is the outer castle level, whose bg looks like it's solid. Still a good hack in terms of aesthetics overall.
As only issue, I point out that music breaks in accurate emulators.
I would've loved to see this hack completed. It has some flaws, but it has all the rights to be an outstanding hack in my opinion.