The first problem you face is to define "classic film." There are two concepts of this term abroad. Most commonly know is the colloquial, or everyday, meaning, and it can describe anything from a well liked film to Bobby's favorite new cult film. The second definition is an academic one and was developed by Bordwell, Staiger and Thompson in Classical Hollywood Cinema. They define classical film according to:
- time period (1917-1960),
- narrative structure,
- editing characteristics,
- unified, linear cinematic space and time,
- unifying style in motivations and conventions.
I suspect that your assignment draws upon the colloquial definition as referenced in the question: "How is this a film classic to you?" In which case, your second thesis topic (post #4) seems a good one to me.