1. A house divided against itself cannot stand. Why would a demon explain Godly topics to me?
Personally, I would wager that a demon looking for power would GLADLY take the position of God. That's the reason demons are supposedly so dangerous, because they have the ability to pretend to be God and lead us away from whatever the real God is.
2. Just to write the book.
Would you do anything else "God" told you to do?
3. Of course, plenty of people know God, I am not special.
I'm sure we all know God in our own way.
4. God has the same Plan for everyone, do you wish to know God's Plan?
I've heard it. Personally I don't think the One would actually construct the exact same plan for all of us if it wished us to be unique and actually cared about our spirits. So, no, I'm not interested in a God that has only one plan.