Was God caught by surprise by human history, or did He plan it beforehand?

God was not caught by surprise. Scripture indicates the whole scheme of things was laid out long before the universe was created, and the whole human experience was pre-planned. The plan of redemption was already in place long before Adam was created, with Christ's death, burial, and resurrection according to the Scriptures.

Les explains from I Corinthians 15 that Paul preached what he also received: that Christ died for our sins, was buried, and rose again the third day according to the Scriptures. Les emphasizes that long before the universe was ever created, God already had the whole scheme of things laid out. He was not caught by surprise; the whole human experience was pre-planned, and the plan of redemption was already in place long before Adam was created. Because it was prophesied, all man has to do for salvation is believe it. Les then moves to Galatians 1:8, warning that any other gospel brings eternal separation from God, not merely prison or capital punishment.

1 Corinthians 15:4

And that he was buried, and that he rose again the third day according to the scriptures:

When did God plan the whole scheme of things and the human experience?

God pre-planned the entire scheme of things and the human experience long before the universe was ever created. The plan of redemption was already in place before Adam was created. God was not caught by surprise; it was prophesied according to the Scriptures.