The sleeping dinosaur is an adult Psittacosaurus. It was herbivorous, and snipped off tough plants with its parrot-like beak.
Psittacosaurus could move around both on two legs and on all four, but probably preferred to go bipedal and sprint to escape from predators.
This model of Psittacosaurus shows it sleeping because the fossilised specimen it was based on looks as if it is lying asleep.