1.) its an older no-name rear with a thread-on 16-tooth bmx freewheel and spacers.

2.) chain tession (now dont laugh...) The older Specialized frames have the standard quick release dropouts (small, round and useless for adjusting chain tension). I noticed the dropouts seem to be similar to the horizontal (forward-facing) dropouts, but had most of the "gap" filled in during the casting process. I took a dremel and removed all that excess metal, creating a horizontal dropout. I cant beleive it, but it does work. I figured if I screwed up the frame, what the heck, this was a side project made from junk parts anyway. I suspend the bike by the rear wheel before tightening the axle bolts, and voila- tension. Its still not as tight as I'd like, but it works.

3.) not sure. I'll have to go home and count the teeth on the big ring