Or are we just products of nature with our lives predetermined by our genetic makeup and environment?

Parents affect our free will sadly before birth and afterwards. But we have some free will though

Yes, of course. Some of it is predetermined, but it's how you utilize your predetermined environment and skills that constitutes free will.

No, it's only an illusion.

Free will doesnt exist. Since there is no effect without a cause, all your decisions and all your existence was already set in motion during the Big Bang.

To a certain extent, yes.

I think it's a good thing to advocate

I don't believe in "destiny", "fate", or any of that mumbo jumbo. You make your own decisions and the consequences that happen are purely determined by you and your actions. Sometimes unforeseen circumstances happen, but that's pure probability and chance.

Was it free will to eat that popcorn?

Yes, but what is meant to be shall be.

Determinism only holds true for every event that happens naturally in the universe not to the human mind and consciousness.

Yes!

Determinism explains why without explaining how. The how is you.