This is a very simplified view of an clutch assemblie. Only the most important part, necessary for the operation. (usefull for operation-understanding)
Further on there will be a more realistic assembly.
A diaphragm spring is used because they become stiffer if they wear. Ohter (coil) springs do the oppisite, they become weaker en weaker. This results in a slipping clutch.
Studs keeps the diapragm spring in place. But allows also a little movement in radial direction.