Possibly, though questions about morality or free-will, or the nature of knowledge or whatever, are not.
But what I meant was that almost any question can be considered philosophical under that definition. Until you actually test it scientifically at least. And if that's the case, then the meaning of "philosophical questions" becomes worthless. A word that can describe anything is useless. The value of a word is that it can be used to differentiate between things.
No, that’s not all! Philosophical questions also have to be relevant. That’s a squishy condition but I would really say it’s that simple. There is nothing special about philosophical questions per se, it’s whatever humans find intensely interesting and cannot (yet or ever) be investigated empirically.
(I’m pretty sure I agree with you that something like morality can, at its core, not be empirically investigated, though empirical investigation can help create clarity in arguments about morality, though I’m not sure whether that’s an absolute truth that cannot ever be changed. Free will? Nature of knowledge? Those obviously are ripe for empirical investigation. I don’t see why we should never be able to answer those questions conclusively and empirically.)
I don't know about free will because it depends how you define it and it's not something I've ever understood, though it doesn't seem like a concept that is dependent on how the universe actually is in a physical sense.
The nature of knowledge is pretty vague too, but if you mean the concept of how we can ever know things, that also doesn't depend on how the universe physically is. In another universe with different laws of physics, it would still apply.
"What can be known?" "Do we have free will?" "Does God exist?"
(hint, any question that starts "Do we..." or references questions of existence is asking about the state of reality)