"Dive in head first" is to rush into a situation without thinking.
The head person.
That means answering with the first thought(s) that come(s) to mind.
Stay calm
An idiom is something that does not mean what the phrase says literally, so yes. You can't actually laugh your head off.
To dive in head first or sometimes feet first, means to rashly put all your effort into something without thinking of consequence or reward. This is often applied to new experiences such as careers, relationships, and pastimes. Example: "Jean dove off head first into the dating pool shortly after her breakup with Ted." "If you dive off feet first in a dangerous situation you might get hurt."
To turn completely around and head back in the direction you came from.
Keep an idea in ones head to act on it later.
If used as an idiom, it usually means that you are confused about something. The image is of you scratching your head to try to think better.
A very severe headache, as if an imaginary axe is "splitting your head in two".
The idiom "I lost my head" means that someone acted impulsively or irrationally, often due to strong emotions or stress, without thinking things through carefully. It suggests making a hasty decision or saying something out of anger.
The idiom "a hot head" refers to someone who is easily angered or quick to become upset or frustrated. It implies that the person has a tendency to react emotionally or impulsively in challenging situations.
I think the Runescape developers probably originally envisioned Clarence the wizard's head being found in the sand (head in the sand) but then later realized if you found his head first there wouldn't really be a mystery or quest to solve since it would be obvious who it belonged to, being his head and all. So they changed it to hand but left the pun I guess.