Answer to Question 1
A concept model, or study model, is a rough form that represents the design idea, a 3D equivalent of the concept sketch. Its purpose is to study appearance and relationships. It is usually made of cheap, easy-to-work with materials.
A prototype, or a quick study or working model, may look somewhat like the finished product, or identical and functionally equivalent to it. Cheaper materials than what are ultimately planned are used because the prototype's purpose is to solicit feedback and change. Custom furniture and door makers often make prototypes of cheap wood, with applied swatches of different finishes.
A finish model, or presentation model, shows exactly what the final product, room or building will look like. It is to scale and contains accurate details. Finish models vary in appearance; elaborate ones are often publically displayed.
Answer to Question 2
C