Generally stars are in the one galaxy. However, it is possible for galaxies to collide or merge, so in those instances it can change.
No, there are more massive galaxies with stars in them.
A "Galaxy"
A galaxy is by a definition a group of stars. If there were no stars it could not be a galaxy.
All stars visible with the naked eye are in the same Galaxy. Our galaxy, the Milky Way.
Every galaxy contains stars, if that's what you mean. "Galaxy" means "big bunch of stars". No stars ===> no galaxy.
there all made of the same thing
Halo stars are usually very old stars that do no orbit the centre of the Galaxy the same way that our Sun or other stars in a galaxy. Rather, they travel in elliptical orbits, which often take them well outside the plane of the Galaxy.
Elliptical Galaxy The Elliptical Galaxy has mostly old stars and blue stars are new stars.
The sun is a star but the sun is a star but it is the only one in our galaxy, the milky way.
Venus is in our solar system and so it is in the same galaxy as we are. We are in the Milky Way galaxy, as are all the stars that you can see.
Bellatrix is in the same galaxy that we are in: the Milky Way. All the stars you see at night are in the Milky Way.
If it didn't have stars it wouldn't be a galaxy