Does changing the classrooms' names matter? At first it was 1-A and 1-B.
No actual reason for you to change it. Just an option if you wanted to name them something different
Why is Suzie, Simon, and Sophia/Reginald all have different surname? Aren't they are supposed to be family?
They're not a family. No where in the game does it mention as such. They have different last names (Except Sophia & Reginald because they're married) because they have no relation to each other.