1) Technically, specifically, I can't say. I would guess it's a switch that you make to advance to the next gear.
2) So more folks would buy their cars. Lots of people don't like to shift. Especially nowadays when cell phones are so poopular. I've heard guys brag about having a Tip.
3) Pretty sure the 964, if earlier it may have been the 928.
4) Easier to drive. Less effort from the driver when in auto mode but one can switch over and get a few jollies from "shifting".
And that's not a typo.
Oh, since this thread is in OT, let's see the Volvo. I have a 95.