Daniel got the job because he looked like the description of Harry as created by Rowling. The fact that Daniel has blue eyes and Harry has green eyes didn't bother Rowling as long as they gave Lily blue eyes as well.
He wasn't really an actor, at least not on that scale. So, for the first movie, he was playing 'Daniel Radcliffe' and not 'Harry Potter'.
I've always wondered how people got into Diagon Alley. If Hagrid had to reach up with his umbrella to tap the bricks, how in hell were 'normal' people supposed to reach them?