Can a UIView not have a layer and vice versa?

No, it cannot. Every UIView always has an associated underlying layer of type CALayer. It is provided by default and manages the visual presentation and behavior of the UIView. Conversely, it is also impossible: a CALayer cannot exist without an associated UIView object in the context of display on the screen within the UIKit view hierarchy. CALayer provides data and methods for drawing, animation, and geometry management, while UIView acts as a wrapper, handles user interactions, and manages the view hierarchy.