A class Rectangle can be whatever you want. You can overload it. You can change everything including how it’s rendered. It doesn’t have to be any of the things you list.

A div element is a node in a tree which will be rendered by your browser in the way specified by the spec. You absolutely can’t freely do most of the actions you list to a div. There are severe limitations.

A div doesn’t at all emulate a class. Its semantically something completely different.