Poser

noun

1. A particularly difficult question or puzzle.
2. Someone who asks a question or sets a problem.

   "Even as a child, she was a habitual poser of difficult questions."

3. Someone who, or something which, poses; a person who sets their body in a fixed position, such as for photography or painting.
4. A poseur; someone who affects some behaviour, style, attitude or other condition, often to impress or influence others.