Do all of the blades need to be directly attached to the central disk or can they attach to a structure which is attached to the disk (such as a cup), to create multiple layers of blades?

Rule 3.a states the blades must be attached to the central disk. Since the rules do not state “directly attached to the central disk” then this would be allowed by General Rule #1. However, any structure attached to the CD/DVD is considered part of the blade assembly and, as such, must comply with the construction parameters.