Probably still important, in the sense that a head start is a head start. If a Stanford graduate goes to Google after senior year, their whole career is likely to look a lot different. Steps lead to other steps.
Much less - then you get to the same brand name effect but for companies you've worked at. Though those brand names probably correlate a lot more heavily to real employment value.
A lot less for sure. I've met many top 10 university graduates who are 30+ and have nothing to show for it with little respect in their domains and mediocre job prospects. It certainly is a massive help in the early 20s though.
