Number four is overreaching. If we had solved the "what is knowledge" problem, AI would already be a reality. The "answer" you give is at best a clearing away of one source of confusion.
I'd consider "the origin of life" a solved philosophical problem.
I'd consider "the origin of life" a solved philosophical problem.
I think one could say more generally that the first cause problem has been solved or almost solved, in the first sense that Yvain described. I am not a physicist, but from what I can tell, physicists are finding it less and less necessary to worry about the next step in an infinite regress.
Philosophy is notorious for not answering the questions it tackles. Plato posed most of the central questions more than two millennia ago, and philosophers still haven't come to much consensus about them. Or at least, whenever philosophical questions begin to admit of answers, we start calling them scientific questions. (Astronomy, physics, chemistry, biology, and psychology all began as branches of philosophy.)
A common attitude on Less Wrong is "Too slow! Solve the problem and move on." The free will sequence argues that the free will problem has been solved.
I, for one, am bold enough to claim that some philosophical problems have been solved. Here they are: