User blog comment:Kevo411/More Hunter x Hunter Questions/@comment-14902757-20140916080130

1. I can't remember how or where I got this answer, if it was from a certain episode or a discussion with another fan. But what I have in my head for an answer is that back then, every time Killua wanted to fight, he used to feel this (sharp) pain in his forehead and so the "practical thing to do" was to remove that which causes the pain. So he stuck his fingers into his head and removed the cause of pain.. He didn't initially know that there was a needle there but he knew there was something foreign in there, he felt it. I'll see if I can find what episode it was but if couldn't then that might mean that I ended up with this conclusion after having a discussion with someone else.

2. I honestly don't see why not? It's an ecosystem that exists even without humans around.

3. I already asked this here. Question number 6. The thing is there are really hunters who are poor at using nen. Examples are the players in the GI game, the hunters who attacked Canary/Zoldyck Estate. Also, it was never mentioned at what stage in the exam he became an examiner, could very well be sort of in the pre-lims. Finally, there are no specified requirements for becoming an examiner.

4. The only person who could have heard Majitani was Kurapika who during that time was consumed by rage. But I agree with you, the cameras should have been able to capture what he said. In Yu Yu Hakusho, when Kuwabara whispered the forbidden word inside Kaito's territory, it registered as having said the word no matter how inaudible it was. Maybe this is a subtle cross-referencing on Togashi's part.

5) Applicability of techniques varies. He wouldn't have used it against someone who can easily see through and fend off his attack (called "snake awakens". I believe he's able to instantly quantify his enemy's capacity and chooses from his arsenal of moves accordingly.

6) It is a short-range,  point-blank form of attack. It also works more effeciently if the enemy already knows about rock. Rock gives his paper and scissor the element of surprise so sometimes he might not even get to that part if rock already finished off the enemy. Also, again applicability in battle.