I haven’t made a study of Hitchcock so I can’t comment on the first two questions. As for the third this was an amazing start for a first-time director.
The voyeuristic scenes set up the vulnerability of the women; then the scene where the dancer meets the rich man shows her toughness. Later when we are introduced to the woman looking for a job we see her naivete and helplessness and see the dancer sizing her up.
This sets up the entire movie.