Population II stars are the oldest in the Milky Way. These stars formed from the remnants of earlier generations of stars, and they have lower metallicity compared to younger Population I stars.
Population I stars
Population 1 stars are metal rich stars. See related question.
Population I stars (metal-rich stars) are common in the Milky Way's spiral arms; Population II stars are more common in the galactic halo.For more details, you may want to read the Wikipedia article on "Metallicity". Note that in astronomy, "metal" is an informal name for elements other than hydrogen and helium. This usage is quite different from the usage in chemistry.
Yes, there are young stars in the Milky Way Galaxy.
The Milky Way is a huge group of stars, somewhere between 200 and 400 billion stars. The stars themselves, or the Milky Way in its entirety, is not in line with anything.
The so-called "Population I" stars are found in the galactic suburbs, which is where we live. Population II stars are concentrated toward the galactic bulge.
The Earth is in the Milky Way Galaxy. We can see stars at night, so yes.
The milky way is not a constellation
The Milky Way is our galaxy.
No, because they are not. Sirius A and B are just two stars in a Galaxy of many billions of stars. Sirius is a few hundred million years old, younger than most of the stars in the Milky Way.
Yes, the Milky Way is much larger than the sun. The Milky Way is a galaxy containing billions of stars, including our sun. The sun is just one of the many stars within the Milky Way galaxy.