Question: If someone is a kafir, does it mean they don’t believe in God’s existence?

Answer: According to the Qur’an, a being can believe in God’s existence but still be a kafir because a kafir is someone who opposes the truth even though he or she may acknowledge its truthfulness. 

Question: Does the Qur’an ever call the Devil a Kafir?

Answer: Yes, in Q2:34 

Question: How is the Devil a Kafir in the Qur’an?

Answer: By rejecting God’s commands 

Question: Where does Kufr come from?

Answer:  Arrogance, that is, thinking you are above the God’s commands.  

Question: Since Iblis or the Devil is a Kafir, is possible that he stopped believing in God’s existence?

Answer: No, he fully experienced God before his fall. He is 100% certain that God exists.