I am not here to mock Christianity but just here to understand some knotty issues.

If the devil caused Adam and Eve to sin, who caused the devil to sin?

I heard my pastor calling the devil a greedy spirit who in spite of being chosen the greatest among the other angels still wanted God's throne.

If the devil was so beautiful and so perfect and created by a perfect God and lived in a perfect gathering of a perfect God and other angels, how then did sin (an imperfection) enter into the perfect scene?