Positive charge lug off the rectifier. The alternator is grounded through the housing.
Yes. It also makes the pulley size (crank and alt.) critical to accuracy.
I can't help without a specific application and a diagram, and I have neither. Typically, the alternators are either 2 or 4 wire connectors (4 place, with only 2 used, in the 2-wire). One is the field exciter, the others are for voltage regulation and the tach (if the correct application). I don't know the colors, but I bet google does.