Question

why are some constellations visible all year? why are other constellations only visible during certain seasons?

Answer 1

Most constellations are visible about 300 days per year. Only when the Sun is very close to that constellation is it entirely hidden. But since few of us get up before dawn to study the sky, we typically see only "evening" stars.
Some constellations, such as Cassiopeia and Ursa Major are "circumpolar"; they are close enough to the celestial pole that they are, depending on your latitude, always visible.