Thank you for feedback!
I fixed that problems today ( with walls and double slimes in one tile) , but probably the game has not been updated yet on Crazygames.
With the saves, this is my mistake, I forgot to change the name of the "saves file" in the second part, and now if you go to the first, the saves in the second part are erased. And it seems I can't change it, so as not to delete the saves for those players who have already started playing.
I also thought about redo / undo, but it seemed to me difficult to do this with an almost finished game. had to think about it before starting development :(