are we capable of perfect,unchanging,and permanent knowledge? how did plato address this concern?

Answer 1

No. But, the larger question is whether perfect, unchanging, and permanent knowledge is possible at all, and not whether we are capable of having it. Plus, what do you mean by "perfect," "unchanging," and "permanent?" And, then there is the question of what you mean by "knowledge." Do you mean that knowledge is Justified True Belief, as Gettier said, or do you mean to say that knowledge is something else? The question you ask is truly a massive question for many different reasons, and requires a large discussion before it can be properly addressed.

We traditionally view the Allegory of the Cave to be Plato's answer to a much more simplified version of your question, though the Allegory of the Cave is rife with its own problems, the largest of which is how one would even access the realm of the Forms from outside of it, and how, in a perfect realm in which there is no change, because change implies that perfection does not obtain, is it possible for the Forms to come into contact with anything or anyone in order to be either Known, or known.