"Known Bugs/Errors
-Greenhil Cavern is avaible from the start. (unknown why)"
This is surely because on the world editor you chose to set the first level (green hill 1) as the beginning of the game, it always makes the paths already opened for the next level (green hill cavern) although you haven't completed the first one.
I'm playing it currently, but I don't know if I should since you maybe have already corrected some stuff like the ? blocks height placement.
About the first level : The water tiles making it able for Mario to swim at the end are misplaced at the border, like I'm on the ground near the water (but not in) and you can swim, which is not something you want.
There is this one hole where you can walk on the lower border of the screen, without any visible block, and just near it (like 1 block to the right), there is an actual pit of doom where a jumping goomba with wings fall in :
Then there is a goomba generator which at first sight should protect something valuable, but there is absolutely no bonus in this very little zone, the blocks contain nothing.
Also the background tiles of the SMW end bar are strangely placed (in the second level you've done the same thing with the midpoint).
The levels are VERY short as you said it, you should definitely work a lot more on them before releasing the beta episode because there is not much to say about them (except the errors I've pointed).
Other stuff :
The yellow goombas when they die or are stomped by Mario have the basic goomba animation whereas they should have the custom yellow goomba one. It has something to do with the effect animation of the goombas.
There are cutoffs like for pipes, and corners or ground tiles in Fraglands 2 are fucked up.
In Deep Prismsea, you can skip the little water section by swimming on the top of the screen.
