Free will

Do we necessarily need to either have it, or not have it? Nothing in between? In my opinion no. How much free will we have depends on to what degree we are aware of things which influence our decisions. A person who hears some bad news might hit the table with her fist, and the person might do it spontaneously, completely unconsciously, because this is just her nature. Another person might hear some bad news, she will feel the anger and that she wants to hit the table with her fist, but decide not to do so, because it would hurt her hand.

We are adaptive systems with memory

We process inputs (perceive) and produce outputs (execute actions), i.e. we implement a mapping from inputs to outputs

• adaptive = the mapping might change with time
• with memory = the mapping is not from single input to single output

Inputs which influence our outputs might include even the whole history of the universe, because our bodies were created through the evolution. For example if somebody cuts off my hand, I can't just decide to grow another one (at least not in the present).

• some of our outputs are completely determined by our history
• some of our outputs are subconscious reactions (reflexes, learned, but unconscious reactions), which we might indirectly change during our lifetime, by learning and repetition
• some of our outputs are conscious, which we perceive as the free will

Is completely free will possible?

I don't know if complete freedom of will is possible, but one might think it has something to do with the Buddhist liberation. So my answer to the OP would be: every human has the potential to free will, but the degrees vary from person to person, and can change during their lifetime.