poser

nouns

a person who habitually pretends to be something he is not
poser, poseur
is derived from
pose
a person who poses for a photographer or painter or sculptor
"the president didn't have time to be a model so the artist worked from photos"
model, poser
is derived from
pose
a particularly difficult or baffling question or problem
poser, sticker, stumper, toughie
is derived from
pose