How do you unlock planet d in dino run

You have to do the Insane challenge, but when you are at the big volcano, DON'T GO TO THE SECRET SURVIVAL OR THE PARADISE! If you do then you are never going to unlock Planet D. So just ignore going to the secret survival or the paradise. Just go straight ahead. After you finish the Apocalypse level, you will notice that you had come to another level called Beyond Apocalypse, and there is no background but keep on going anyway unless you don't want to unlock Planet D or you want to be doomed/extinct for no reason at all. At the end, you will see a spaceship. If you go inside, you've unlocked Planet D! The final Super Egg, "Brontosaurus" will also be there!