Why did God harden Pharaoh’s heart? Was it unjust for God to harden the heart of Pharaoh and then punish Egypt for what Pharaoh did as a result of his hardened heart?

Links:

Why did God harden Pharaoh’s heart? - https://www.gotquestions.org/God-harden-Pharaoh-heart.html

Why was Pharaoh so resistant to Moses’ pleas to “let my people go”? - https://www.gotquestions.org/let-my-people-go.html

Who was the Pharaoh of the Exodus? - https://www.gotquestions.org/Pharaoh-of-the-Exodus.html