Does a UX designer need to know how do you code?
No, most UX Designers are not required to code (at least, not at an advanced level). However, it's still to their advantage to develop an understanding and appreciation for what Developers do.
What is manipulative design?
Gamification calls for cogent philosophical analysis and is a valuable opportunity to explore manipulative design, in which users are manipulated into doing something by using an artifact just as it is designed to be used.