There is biblical evidence for God not knowing everything.
Gen 2:
19) And out of the ground the LORD God formed every beast of the field, and every fowl of the air; and brought them unto Adam to see what he would call them: and whatsoever Adam called every living creature, that was the name thereof.
Gen 6:
6) And it repented the LORD that he had made man on the earth, and it grieved him at his heart.
7) And the LORD said, I will destroy man whom I have created from the face of the earth; both man, and beast, and the creeping thing, and the fowls of the air; for it repenteth me that I have made them.
Gen 22:
12) And he said, Lay not thine hand upon the lad, neither do thou any thing unto him: for now I know that thou fearest God, seeing thou hast not withheld thy son, thine only son from me.
Jer 7: (NIV)
31) They have built the high places of Topheth in the Valley of Ben Hinnom to burn their sons and daughters in the fire-something I did not command, nor did it enter my mind.
Gen 2:
19) And out of the ground the LORD God formed every beast of the field, and every fowl of the air; and brought them unto Adam to see what he would call them: and whatsoever Adam called every living creature, that was the name thereof.
Gen 6:
6) And it repented the LORD that he had made man on the earth, and it grieved him at his heart.
7) And the LORD said, I will destroy man whom I have created from the face of the earth; both man, and beast, and the creeping thing, and the fowls of the air; for it repenteth me that I have made them.
Gen 22:
12) And he said, Lay not thine hand upon the lad, neither do thou any thing unto him: for now I know that thou fearest God, seeing thou hast not withheld thy son, thine only son from me.
Jer 7: (NIV)
31) They have built the high places of Topheth in the Valley of Ben Hinnom to burn their sons and daughters in the fire-something I did not command, nor did it enter my mind.
Also, notice that these verses are all from the Old testament, when the tribal theology was quite primitive and very anthropomorphical (my English needs to create words, lol).
In the New Testament era, during Greek higher philosophy, there are no such statements.
God knows everything that is available to know, but it is not possible to know ahead of time every decision we as free will beings will make before those decisions are made.
Simply accept it as true.