Is the constellation 12 named after the stars in the sky?

Constellation is the sky area divided by the ancient Greeks according to their mythological imagination. Now the whole sky is divided into 88 constellations. 12 constellation is one of the 12 constellations on the ecliptic (that is, the orbit of the sun). Contrary to what you said, not all constellations are named after the stars in the sky. But stars in the sky are named after constellations. The brightest star in the constellation is generally called "xx Alpha" star. The second brightest star is called beta, and so on. As we are familiar with Vega, it is called Alpha Lyra. Polaris is alpha in Ursa minor.