Is the book I won in the competition lawful for me, given that I did not adhere to the condition of listening to the educational clips before the test, and what should I do with it if it is forbidden?

If listening to the educational clips was a condition for entering the competition, and you did not listen to them, then it is impermissible for you to enter or to take the prize; because the Prophet, peace and blessings be upon him, said: "Muslims are bound by their conditions." Since you won the prize, you must seek absolution from the organizing body of the competition by informing them that you listened to the clips subsequently. If they permit you to keep the prize, then that is their right. But if they ask for its return, then you are obliged to do so.