Yes, God knows everything that is possible to know. But the future doesn’t exist, and therefore there is nothing to know. The fulfillment of prophecies are not certain; they are but predictions based on what IS known, but prophecies, even those uttered by true prophets of God, don’t always come true. Doubtless God inspired Jonah to prophesy, “Yet 40 days and Ninevah shall be overthrown!” Forty days elapsed, and Ninevah was NOT overthrown. Yes, I know the reason—the Ninevites repented, and so God changed his mind and did not overthrow Ninevah. It seems at the time God inspired Jonah to utter the prophecy, he had expected that the Ninevites would NOT repent.
It is not possible to know in advance what a free-will agent will choose in the future. If someone KNEW in the absolute sense, that you are going to eat an apple tomorrow, then it is now a fact that you will eat an apple tomorrow. Therefore it is impossible for you to refrain from eating an apple tomorrow. And THAT would imply that you will not have the free will to refrain from eating an apple tomorrow. Thus it is a logical contradiction for anyone to KNOW in advance what a free-will agent will choose.
Even God, who is omniscient, has sometimes thought his people would do one thing, when in fact, they did another. Here is an example:
Then the LORD said to me in the days of Josiah the king, “Have you seen what faithless Israel did? She went up on every high hill and under every green tree, and she was a harlot there. I thought, ‘After she has done all these things she will return to Me’; but she did not return, and her treacherous sister Judah saw it.” (Jeremiah 3:6,7 NASB)