#2
Chords don't define a genre, and you're in the wrong forum. Head over to MT if you must, but I beg you, just google it.
#4
It's true that the key dosen't define the genre, but A is a pretty popular key for blues. I use Am7, Dm9, Dm13, Em9, Em13 for a basic 12-bar in A. The 13th chords are just kinda a fill but they sound cool.