Well, “If I had an hour to solve a problem and my life depended on the solution, I would spend the first 55 minutes determining the proper question to ask… for once I know the proper question, I could solve the problem in less than five minutes. Albert Einstein(1.)
In my opinion, the titles of science papers are so dominated by answers that you would be balancing the yin and yang cosmos by using a question in a title;-). I say this jocularly but there is an element of truth. Research in the hard sciences seems to be eternally dominated by men. Why then would questions be relevant? In her book, He said she said, Lilian Glass (2) observed in mixed conversations of men and women, the women mostly listened, but when the topic of conversation turned boring or uninteresting to the women, they would ask a question and all the men seemed to jump to answer. Thus the women appeared to subtly control but not dominate the conversation. This seems to be the case for the hard sciences where the answers seem be territories to defend, and questions: signs of weakness. Indeed, stamping out or hiding questions unsolved seems to be rampant in small and even large domains where a camp of experts rules.
No, as thesis consists of normally 3 to 6 objectives which are research questions in nature. if you put thesis as questions your objectives may not linked to thesis name
For me why not as long as it is a broad question and could be answered by how and why. once you asked this broad question you opened lots of sub-questions to answer it.