there actually is a rare brain disorder in which the person affected by it has no fear.

yes but TBH if you experience zero fear something might be wrong and it might be time to see a specialist

Fear keeps us safe. It’s a natural response. Why would we want to be rid of that?

Yes

Yes, but it might depend on who you are/how your personality developed. I think, though, that ultimately any state of mind is possible. I know I'm unafraid of some things that other people are afraid of, and I've been unafraid of things that I'm normally afraid of, and also things that everybody is afraid of, while I've been psychotic. =P

I don't know. I never experienced it