Yes, a question can be answered without signing in, but not signing in means you do not get the contribution points, and the last edit would show up as an ID rather than your user name.
A question that isn't supposed to be answered is called a rhetorical question.
No one. Such questions, without a referent cannot be answered
Rhetorical question
The question cannot be answered without the context.
Your question cannot be answered without context.
This question can't be answered without knowing who is meant by "he" and "them".
Without more information, this question cannot be answered. Who is the she and who is the you?
Without more information that question cannot be answered
Who is that he? Your question cannot be answered without the basic information.
Without a world census this question cannot be answered
No, if a question has no answer how is it possible it has been answered?
Without specifying an "it", the question cannot be answered.