The prequel trilogy certainly re-cast some of his actions in the original trilogy ("Wait--he knew this all along?"). And then his drama-queen "shutting himself down after Luke disappeared" act in TFA? Unacceptable.
That's true, and Vader was the first one to appear once Palpatine became Emperor. Maybe people just shrugged and figured he'd been around for a while. Palpatine's Sith history wasn't common knowledge so I doubt anyone considered his prior apprentices at all.I suppose that it's entirely possible that only Obi-Wan and Yoda knew that Vader was Anakin. Other Jedi probably knew but they had all died or disappeared.
It is an intriguing question, though. Vader just sort of shows up as the Emperor's right-hand guy/enforcer at the end of Ep.III--doesn't anyone wonder where he came from? I wonder if there will be any nod to that question in Rogue One.
I don't know that we have had any concrete clues, but the intarwebz is abuzz with theories about multiple timelines and just about everyone on the show being some sort of robot, both inside and outside the park. I guess only time will tell.
That is an interesting question. If Leia knew that Vader was Anakin Skywalker, why didn't she (or anyone else in the Rebellion) say anything when she met Luke? At the end of Episode III, when Vader steps up and stands at the bridge of the star destroyer alongside Palpatine, is it supposed to be understood that this shiny new guy is Anakin? Or was he just "that new enforcer for the Emperor"?