What are the largest and the smallest constellations in the night sky?
No matter what everybody else says, Hydra is the largest constellation and Crux is the smallest.
Due to the rotation of the Earth, the constellations overhead in the day time (which are not visible as it is) are not the same ones visible at night. However, the constellations in today's day sky are the same constellations in the night sky 6 months from now, and the constellations in tonight's night sky are the same constellations in the day sky 6 months from now.
What motion is responsible for the regular seasonal changes of the constellations visible in the night sky?
You had an actual grammatical question going there right up until the end. It's actually impossible to answer, since "circumpolar" constellations (such as Ursa Minor for observers in the northern hemisphere) are always in the night sky, and other constellations (such as Crux for observers in the northern hemisphere) are never in the night sky (or the day sky either, for that matter). Zodiacal constellations such as Aries are approximately on the celestial equator, and…