What is the correct usage of this site? Should I be using this for all my CS50 questions, or are some not allowed? What about overlap with Stack Overflow?
I'm gonna quote What topics can I ask about here?
If your question is not specifically on-topic for CS50 Stack Exchange, it may be on topic for another Stack Exchange site.
Of course there's an overlap with Stack Overflow. I like thinking of this site as a more beginner-friendly Stack-Overflow-like website. This site probably has the first priority for questions that are mainly about the course's materials and/or psets.
It's probably easier/faster to get answers for such questions here than on Stack Overflow since technically most (if not all) the members of this website already took/are taking CS50.
Keep also in mind the "Academic Honesty", it is defined here.
What about overlap with Stack Overflow?
In my opinion, this is a sub-site that is specific to CS50. How did I arrived at this conclusion? I copied one of the questions posted on this sub-site and did a Google Search. Result showed up from single source, i.e. here. So there is no overlap.
All questions imo... Not sure about the overlap.