Is it blasphemous to think God knew Adam and Eve would sin…because He is God and yet He punished them?
This is a good question. The short answer is no, it is not blasphemous to think God knew that Adam and Eve would sin. Yes, He knew they would sin and that He would punish them. Indeed, Scripture makes clear that God knew they would sin.
As this passage makes clear, God chose those who would believe in His Son and be saved (v. 4). Since He chose us before the foundation of the world, that means God knew that we would be sinners and that God would need to send His Son to provide salvation. This means He knew that Adam and Eve would sin, since we are sinners because of Adam’s transgression.
This does not mean God caused Adam and Eve to sin. God’s motivation in creating Adam and Eve, knowing they would sin, was always with the death, burial and resurrection of Jesus in mind. Man’s fall and ultimate redemption was always God’s plan when He created all things, including man. Somehow, God works through our evil, but He does it for good (see Genesis 50:20).
Part of the reason for the Fall of man is so God could demonstrate His many attributes: love, mercy, justice, wrath.
Speaking of God’s sovereignty in salvation...
Here we see that unbelievers (vessels of wrath) make known God’s wrath and power, while believers (vessels of mercy) make known God’s mercy and glory.
God declares the beginning from the end.
We may not fully understand all that God does, but it is always for a good purpose, for everything He does is, by definition, good.