Yeah John, what’s up with the only 136 stuff. You very likely could qualify for Mensa :)
But the essence of your Q is hard to define precisely. This is the old ” Nature vs. Nurture” debate.
I know from experience teaching third grade that not everything is set by first grade by a long shot.
There is also a difference between personality and behavior. A fearful child definitely can be taught better skills to overcome their natural tendency and will most likely be better at coping with life than a child whose parents did not focus on that type of training. It is not going to reverse their basic tendency but rather modify it.
Anyone with sufficient motivation can change their behavior patterns at any age. That doesn’t mean it happens easily but it is certainly possible.
There have been some interesting studies done on people with an extreme need to participate in daredevil type of activities.
This becomes especially problematic in the teen years when they begin aping stunts on YouTube emulating the Jackass TV programs.
Some have been permanently crippled or died as a result. And there are some who are drawn like a magnet to that stuff and it seems to have a lot to do with brain chemistry.
Parents of kids like that are at their wit’s end trying to deal with it. The best advice seems to be to first recognize it as an integral part of their personality. It won’t go away, but can be managed with better judgement and appropriate skills.
Helping them find an activity or sport that fulfills this need, while channeling it with some training and boundaries works better than simply banning them and hoping they aren’t sneaking behind your back.
They may even end up becoming an X-games champion or a race car driver or test pilot.
The main point being that this seems to be a genuine need they have for the adrenaline high of risky behavior that will carry into adulthood. Best to acknowledge it and find a channel for it. There will still be above average risk to their choice but at least they will learn some skills to minimize the risk.
So, behavior and personality are separate issues. Behavior can always be modified.