So when you die in Hardcore mode and click "Delete world" you quiting to title menu but your world is not deleted as seen on third screenshot. When the first issue is appeared in menu you do not see the panorama, instead you see gray gradient as seen in the first screenshot. When you create the New World instead of seeing dirtblock background you see what you've seen when you died in Hardcore world as seen in second screenshot. And when you try to join any world you just cant you just see black screenas seen in the fourth screenshot. Everything is fixed by restarting the game. Sorry for all grammar mistakes!