Although the Andromeda Galaxy is a bit larger than the Milky Way, and is large as spiral galaxies go, it is not the largest galaxy. There are larger spiral galaxies, and much, MUCH larger elliptical...
The Andromeda Galaxy is a spiral barred galaxy, similar to our own galaxy, the Milky Way.
No. It is our closest neighboring galaxy.
It's fair to say that our own galaxy was discovered first.
Nothing as far as I know. It is still the same as it has been for years