bones
When you are in the dungeon, just before the fight - you can kill Zombies to get a hatchet as a random drop.
yes
The most expensive drop you can get on runescape is the corrupt dragon battleaxe at 3.9m
parrot
Yaks or Armored Zombies.
920 each
They will attack you, and they can drop loot. see this page: http://www.tip.it/runescape/index.php?rs2monster_id=238
no
The best place to kill zombies is at the armor zombie place. IT is where everyone get 99 str.
till lvl 40
No.
hill giants and hobgoblins drop them sometimes