To qualify as All-Knowing, one has to know all that is knowable (if there is an unseen that is knowable, then God would know it). If something is not knowable, then by definition it is not something that anyone would know. For example, God cannot be expected to know what a gfshks is because gdshks is not a knowable thing. It is just a made up word/label.
God knows what we reveal and what we hide. I believe this amounts to God knows what we would choose in what circumstance and organises everything so that the best outcome happens. Whether God knows what He would choose or not, is not something that is clear beyond that He knows that that which He chooses will be perfect (because His desire/will is perfect). Some relevant verses to consider:
81:29 And you cannot will anything except if it is also willed by God, Lord of the worlds.
7:156 "And decree for us good in this world, and in the Hereafter; we have been guided towards You." He said: "My punishment, I afflict with it whom I chose, and My mercy encompasses all things/wills. I will thus decree it for those who are aware and contribute towards purification, and those who believe in Our revelations."
Imagine One taking into account all things/wills every second and then coordinating such that Existence is Perfectly Existing such that everything is progressing towards what it ought to.
51:47 And the heaven We constructed with resources, and We are expanding it.
That One being knows what all other beings reveal and hide and coordinates/wills accordingly. I think you should also have a look at the following Biblical verse: Hebrews 4:3-5.
To my understanding, God is not beyond time and space. There is no beyond time and space. God is the Omnipresent, so God encompasses all time and space that flows, and God is the flow-er.