:angel:two stuff i dont get...*spoilers*
1) why at the last part, chpter flaw in the plan, the house elves were using knives and pots to attack the death eaters stabbing them in the leg?
i thought they had extraordinary magic?
2) why was malfoy able to cast the petrificus totalus spell on harry in Half blood prince in the train? i thought his cloak is the spell immune one?