You don't have any music, but I'd suggest using Hop! Hop! Donut Lifts because it's the music that was playing in my head as I played the level, and it's already inserted in the baserom.
The midpoint doesn't work.
+The ski section; I thought it would be funny to replace that problematic falling level with a "hidden" falling level. Hopefully I won't have made this for nothing. All the custom blocks are done and the rest of this section should be pretty straightforward to make. You lose time by going outside the flags btw. I plan on adding more obstacles like firs and tree trunks if I can have more resources. I'm already using quite a lot for this level, hence why I'm not sure if I can.
This is very clever.
Anyway, my thoughts on the first half:
It's extremely confusing. I read the message box but I had no idea it was talking about yoshi coins. I thought it just fined me five coins every time I walked into the level or something. Also, if I had known it was talking about yoshi coins, there was no way for me to make the connection that the yoshi coins were used to get into the door under the entrance either. Also, you need to get rid of that exit level through sides generator. This is testing, but it is annoying. Overall, I feel that forcing the player to get the yoshi coins is not fun. Yoshi coins are supposed to be a bonus, not a requirement. But also it just seems like unnecessary difficulty. You have this interesting gimmick of sliding on ice and instead of using it, you do a yoshi coin scout. On the subject of yoshi coins, I couldn't find the hidden tofu block for the first one no matter how hard I looked, the second yoshi coin seems too hidden (maybe a bigger arrow would be good or something because I guarantee most people will just get it by accident), the tofu block for the third yoshi coin is too hard to find and someone would probably only find it by chance because there is no indication, the fourth yoshi coin involves an esoteric glitch that people again will figure out by accident and be mystified by (and the fact that it's abusing a glitch at all is bad in the first place), and the last one is probably the best but it involves figuring out to use that rex that most people will kill upon seeing before even knowing that there is a yoshi coin and then becoming confused. These yoshi coins are too hard! Again, I don't think forced yoshi coin hunting is not good for level but even if it's optional it's still too hard in this level.
My recommendation is to completely redesign the first sublevel. You have this very interesting idea with the sliding block, but it is wasted. Firstly, I don't think it is conducive to the scrolling because it involves not being able to go certain ways and the scrolling incapacitates you from being able to see what you can and can't do. Instead you are forced to keep going at the same uncomfortable speed and inevitably be trapped on a slope. With this slope, you should be able to take your time. Try something that makes forced-sliding interesting. Right now it is just used to keep you from going in places which is as good as a wall in your way. Try something like a plinko machine or something. Or maybe just general sliding fun where you go downwards and then there are some laces to jump off. I think this level has a lot of potential, and you could really utilize it. Just try to make the sliding blocks fun in some way.
Oh also if you need map16, just claim it.