Once the user locks (which most of the users I believe do) the screen rotation function, then there is no way to rotate the Camera. So what to do now? I researched for a couple of hours to do that, I even ask my boss and my senior, and apparently they do not know the answer. I was surprised, or they were just so lazy to help me at that time. The answer again is to use core motion.
Good news: I've already made a tutorial for the core motion.