***** NOT A TEACHER *****
(1) Yes, sometimes you don't use a question mark for a question because it is not really a question. It is a super polite order.
(2) For example, your boss might write this to you: Would you please come to my office. A question mark is probably not necessary because it is not a real question. The boss is really saying: Come to my office now!!! But that is not polite, so he gives an order in the form of a question.
(3) "Would you mind talking more quietly." = Stop talking so loudly!!!
Student or Learner