Tip: You can use Lunar Magic's Overworld Layer 3 Editing system to edit or create your own layer 3 images (castle bricks, fish, rocks) and apply unique effects per level via the Layer 3 Bypass in the main editor.
The title screen has this weird garbage tile. I suggest removing it with this patch. Also, you have some sprite memory issues. I also changed the difficulty to Kaizo: Light since it's more appropriate for this hack.
Overall, this is a short but alright puzzle hack. I could find a lot of solutions, one of them being how you can use the throw block and the shell from the ? block to feed the baby Yoshi or even all five edible sprites. You can get trapped forever if you get past the throw block at the top and just stay still! I'll let it slide, but please get that fixed in future versions if possible.