World Generation Bug, Crashes and Frozen Screen Bug

1. World Generation Bug+:+ So when I was in my world walking in my survival world I saw a double tall grass block randomly floating in the air with a floating 10x6 structure of grass block, at first when I saw this weird thing I was confused then I just left it, fix the bug!
2. Crashes: When I start Minecraft, my game crashes for no reason its very annoying, FIX THIS BUG.
3. Frozen Screen Bug: When I join servers or my friend's world my screen freezes