#1
So what bands constitutes as Alt Metal? What are the qualifications of such? The heavy riffs? Angsty lyrics?

I say most of the these bands could fit in the genre:

Alice In Chains
Faith No More
Sevendust
Jane's Addiction
#3
How about Tool? They have been thrown as Prog Metal and Alt Metal by labelers? They seem like a heavy version of Muse in some cases, though Tool has been around way longer.