FPGA.

See https://en.wikipedia.org/wiki/Hebbian_theory

The way I would put it is that all those different neurons with different kind of receptors on that are so "colored" that there are a set from one place to another so there is an overall gross wiring diagram in that a green bundle of wires go from the limbic system to the frontal lobe but the detailed wiring plan is not encoded in the DNA the way a CPU or an old school television set has a plan -- there is not enough data in the DNA to do that. Instead the brain self-organizes the detailed wiring by learning.

So what you seem to be asking is, can the environment and lived experience affect the structure of the brain, or is it fixed at birth? My understanding is that brain structure is malleable, at least at the neuron level, and that there are lots of measurable changes throughout life, many of them caused by our learning and experience.

FPGA without question.

Completely flexible.

I will use an analogy of consciousness and the mind, take from it what you will. I have written elsewhere about “quantum holography” being a part of our minds and consciousness.

The mind is as a car, and our consciousness the spark that passes over the spark gap. Yes, Zarathustra and by proxy Nietzsche are inspirations yet there is a more literal point.

By the quantum nature of consciousness, an inverse hyperdimensional hologram of the car would flash in the arc of the spark gap.

By tenacity of will (determination of resolve, in the moment of now) one may bias the potentials of that holographic projection such that the embodiment of the car will “optimize.” With persistence and vision the self may be slowly yet gradually restructured in accordance with will.

The trick is having the right “information” (vectors and their unique vector spaces.) I found that before the Internet, even modernity, there were abundant stories of great characters and their mental capacities. Those most interesting are those who lived the most full lives.

Self is a technology of consciousness.