Have you tried using interactions? Create an on page load interaction for section 4 with an initial state as required. Then create an on mouse click interaction ( you will need a timed animation for click 1 and click 2). You can add this interaction to all of your sections.
If you want a nice 3d fold effect , I think you may want to enclose section 4 in another div and set a parent perspective on that⦠I will try an do a demo if you are sure you want this fold effect?