You don't put a Shimano crank on your otherwise Campagnolo equipped bike ...
I would, presuming it were functionally compatible. Or maybe a Campy crank on a Shimano bike.
Wearing a pro kit is bad, wearing a pro kit 2-4 years old is worse, but riding a vintage pro kit on an appropriate bike (some exceptions here and there) is usually pretty cool.
So as the age increases, wearing pro starts from being bad, and it gets worse, but if old enough ("vintage") it eventually gets pretty cool. So is this badness a unimodal function of age (starts bad, gets worse until reaching the maximum badness, then gets better and eventually cool)? Is this a continuous function of time over its whole domain, or is there a step function in which it keeps getting worse until X years old, then at X years plus one day all of a sudden it is considered to be vintage and discontinuously jumps to pretty cool? Perhaps X is not determined in years per se, but as the boundary in time marking a particular era?
Yes, wearing any pro team kits if you are not riding for that team makes you fred.
rustychain kind of hinted at this, but what is the definition of kit? What if you are only wearing a single article of pro team clothing? I sometimes wear an old Pro Tour (or equivalent before there was a Pro Tour) jersey which I obtained at deep discount in a markdown bin a couple of years after the team folded. Does that make me a Fred?
I could argue that you're a Fred for using the term kit. Back in the day, no one called that stuff kit. There was a jersey, shorts (or maybe skinsuit instead of separate jersey and shorts), and maybe gloves.