Okay, First things first I'm assuming your new to game development based off the fact this is a scratch game and that scratch is a platform for kids so i will definitely be treating this as a scratch game and not a Proper game engine Game.
First off right off the Bat the game Gets significantly more difficult at level 2 and 3 and i had a tough time beating them, But one more thing i realized is that this is in Truth just a spam simulator and i was fine by just pressing Space again and again, And it would be fun to introduce other mechanics such as Walking and running and blocking attacks, And more enemies. But considering this is a Jam Game made on the scratch platform (and that your most likely a kid who wants to get into game dev) this is great and honest work. Although i would suggest that if you are serious about game dev as a career and are old enough then you should Switch over to the Unity Game engine or even simpler Godot/ GDevelope as its quite lightweight and Its pretty beginner friendly, Don't spend time on scratch if you know the basic scratch fundamentals because in the game dev world scratch just doesn't translate well.
As for the game: Rated 9/10 ( For a scratch game :D)
I hope you find success in every game you make in the future 😁 and remember, Don't be discouraged by anyone, Every dev starts out somewhere and even i started out in scratch :D
Nope, Its 100% free and the only times you have to spend money is if you need to buy custom assets from someone else (But u can probably find some for free anyways) and if you need to switch the software to dark mode then you need to pay some money then as well (I hate Light mode), and if you need to get rid of the watermark that appears at the start of your unity game. But Yeah other than these 3 small things its totally free and pretty easy to get used to and its one of the best and most Friendly Free 3D engines out there if you want to make actually good 3D games (Godot is more for 2D and their 3D is really bad in my opinion)
Hope this helps :D