Was Satan ever an angel? Why did you become a demon later?

Satan used to be an angel, but because of his pride and arrogance, he fell. Since he betrayed God, he has become evil. He took God as an enemy and tried his best to prevent him from working for people, but he was limited by God's rights and could only do what God allowed. All angels, whether they are good or evil, must explain before God. God knows Satan, because Satan is also a creator, and he is made by God's hand just like us. Satan believes that people who believe in God only believe in God when everything goes well, and only believe in God in order to get something. So he believes that as long as people who believe in God suffer setbacks and pains, then faith will naturally disappear. His power is very limited. He can only create some false things to confuse our hearts and keep us away from God. As long as our beliefs are true, Satan can't do anything about us.