you should just seperate the game into different sections so you can play on broswer, like make the fourth level it's own thing and cut the other 3 but keep the 3 on a different version of the game. You get what i mean?
That sounds like a headache for the developer. It's just easier for them to keep it at a version that can run on browser with as much content available for you as possible and if you like what you see, you'll download the game.
I still don't see why we can't have the level 3 gallery. I mean, those animations already exist, and new pngs for the game over screens don't take much space. It'll still run. And I've run SCRATCH GAMES bigger than this on a chromebook with the processing power of a toaster.