1) Warden is blind but it can tell where you are based on sound and it is found near blocks that scream if you come near.
2) You need to sleep or phantoms will attack you
4) give an allay (the blue flying thing) and item and it will return with more
5) the pink thing kills squid and fish
6) The glow squid can be killed and the ink makes glowing signs.
7) the ocean has sunken ships w/ loot but also weird cyclops fish that shoot lasers at you and zombies that throw tridents
8) the nether got major revamp (new structures, biomes, and mobs)
9) Pillagers (evil grey villagers w/ crossbows), there are related varieties w/ axes and one type that summons jaws and flying mobs but they drop a totem of undying. If you kill a pillager with a banner wait before entering a village or they will attack but you get a be if it if you beat it so be prepared.