Omg ! You are a genius. I was stuck on this problem for three days. I am currently trying to figure out how you did it. Yes, you are right about next part of the problem. Because I couldn't figure this rotation part, I gave linear displacement to top cover to snap fit it into the stack using friction contact. After figuring out your method, I will try snap fit along with it. After that I need to figure out how to produce fatigue for 100 cycles so the hinge as well as snap fit lock doesn't break. Again thank you very much Sir.

- CK