Great questions!
1) For now go ahead and include this in your description, we'll look into making it more explicitly easy to mark.
2) We're going with an "on your honor" type system. Newbies who join the advanced track will be judged against the other entries in there, which is on them. If we see something that looks like it doesn't belong in the beginner track we may follow up with questions about process and methods. A screenshot of the world open on the ipad they made it on, for instance, or how science/astronomy factors influenced their decisions and design. In your example since they're a pro builder they should submit to the advanced track - we're intending the beginner track to be more for those who are totally new to the game or younger children.