Jesus believed the Genesis account of creation. Was He mistaken?

The bad fiction about Jesus is all mistaken, so this part is mistaken too. Both Jesus and the two conflicting Genesis creation myths are just amateurish primitive fiction, so it makes no real difference what a fictional character believes. In "LOTR", Frodo Baggins can say he believes in the Silmarillion, and we know both he and it are fiction. The same is true of Jesus and the Bible.