Good basic tutorial; you just miss a box and enemies tutorial. Good progression system with the missing blocks.
Bugs:
On death there is random % to respawn at the begin of the tutorial. After it happens, on death you will forever respawn at the beginning of the tutorial.
I had strange pixelation on top of the screen.
Design problems:
when you rescue a buddy doesn't update the buddy counter, only when you finish the level. I can understand that, but make a player know how many buddies he has already saved in a level.
A general problem of health pickups balance. We are in level 1, and you put an helm pickup only on the most stupid challenge.
More on health: An open level to explore collides with your old design to have a 2hp system. If this is a collectaton you can't make the player die and restart the whole thing after 2 mistakes (1 for lava). Add this to the respawn bug and the game becomes almost unplayable.
Your demo made me realize how important common coins are into a level. Just imagine a mario level and remove all coins and most of the enemies. You need some short term goals that moves you through the level and make the journey interesting: coins, enemies, powerups etc
In a more general sense, you need to make your levels fun to explore.
Final thoughts, I'm always blunt:
A 2d semiopen world collectaton is a great idea, but I dunno if your game can translate into it. You will need a ton of work to make it viable. Can you really think 3-4 powerups that change the way you interact with a level in a meaningful way? (see mario sunshine/odyseey).
But here comes my bluntness: In my opinion this change is pure scope creep. This to me doesn't seem a genuine attempt to make your game better. Your systems are there, they are basic, but it's not a fault to have a simple game. You need content. You should make levels for your game for a month. A whole month making levels.
Then, if you want, mix them into 3-4 big levels.
If you wanna really try the collectaton route, (re)play the masterpieces of the genre, and then see why copycats like yooka laylee failed.
GL buddy.