I have a couple that sort of fit 3 (in that they involve major life changes, but no princes): The Darkness over Bluemere (http://archiveofourown.org/works/1926702/chapters/4159398) (This one, Cas is the Prince). Wolverines, Windegos, and Winchesters (https://www.fanfiction.net/s/5155714/1/Wolverines-Wendigos-and-Winchesters) (This is one where Dean finds out he's a mutant.) Paternal Evolution (https://www.fanfiction.net/s/7386164/1/Paternal-Evolution) (Dean finds out he has a son and quits hunting to raise him. This has smart!Dean.) Infrangible Road (http://archiveofourown.org/works/218788/chapters/329096) (An AU where John didn't raise his boys on the road but still taught them everything about hunting. Dean goes into the military.) Tony Stark Requests Your Presence (https://www.squidge.org/~peja/cgi-bin/viewstory.php?sid=45543) (Tony tracks Dean down because he wants to hire him. Dean finds out that he did actually get into MIT. This one is short but really good.)
I hope some of these are what you're looking for!
For 4 there's: As You Wish (https://www.fanfiction.net/s/8257066/1/As-You-Wish) which is the only Narnia crossover I've read. SARose is one of my favorite authors. Summary: "In one of many Earths, a spirit calling itself God is trying to block the way to Aslan's Country and relying on humanity to save itself through the Winchesters. The Emperor-over-Sea is not amused. So thanks to Aslan and Gabriel, all parties will get exactly what they want... and almost none will get what they expect. "
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The Darkness over Bluemere (http://archiveofourown.org/works/1926702/chapters/4159398) (This one, Cas is the Prince).
Wolverines, Windegos, and Winchesters (https://www.fanfiction.net/s/5155714/1/Wolverines-Wendigos-and-Winchesters) (This is one where Dean finds out he's a mutant.)
Paternal Evolution (https://www.fanfiction.net/s/7386164/1/Paternal-Evolution) (Dean finds out he has a son and quits hunting to raise him. This has smart!Dean.)
Infrangible Road (http://archiveofourown.org/works/218788/chapters/329096) (An AU where John didn't raise his boys on the road but still taught them everything about hunting. Dean goes into the military.)
Tony Stark Requests Your Presence (https://www.squidge.org/~peja/cgi-bin/viewstory.php?sid=45543) (Tony tracks Dean down because he wants to hire him. Dean finds out that he did actually get into MIT. This one is short but really good.)
I hope some of these are what you're looking for!
For 4 there's: As You Wish (https://www.fanfiction.net/s/8257066/1/As-You-Wish) which is the only Narnia crossover I've read. SARose is one of my favorite authors. Summary: "In one of many Earths, a spirit calling itself God is trying to block the way to Aslan's Country and relying on humanity to save itself through the Winchesters. The Emperor-over-Sea is not amused. So thanks to Aslan and Gabriel, all parties will get exactly what they want... and almost none will get what they expect. "