I mean... There's no way that specific iteration of Under the Red Hood happened in the current continuity. Way too many *major* discrepancies and character inconsistencies.

In UTH, Jason's goals were relatively straightforward. Him having his vendetta against Bruce for not killing Joker. He didn't want Bruce dead, he just wanted to "punish" him and take Gotham away from him. And either A), force Bruce to kill Joker or B), kill Joker himself. The journey to UTH as we know: was Jason going on a world wide batman like tour where he trains under many master class fighters, assassins, weapons dealers, poison makers and so on. In UTH, we also learn that Jason briefly teamed up with Hush, and briefly pretended to *be* Hush so he could mentally mess with Batman before the eventual encounter in UTH, by later switching places with Clayface before Bruce could find out.

From the New 52 standpoint, Jason's goals in this unseen "red hood: year one", you could say, appearantly stemmed from "Bruce leaving him with the joker" whatever the hell that means, and he appearantly wanted to kill Bruce. We also learn that *Nightwing* was apart of the "final" encounter and seems to have played a MUCH bigger role in these events. So much so that he even saves Bruce while he was narrowly at death's door, thanks to Jason and it's not really explained whether or not joker was apart of this version of UTH and we never see him anywhere in the background flashbacks. So my guess is he either escaped in this version or Jason simply never captured him and went *directly* after Bruce with the intention of killing Bruce. Effectively eliminating winick's final stand scene of "you, me and him". Which is completely different to the original story of Jason holding joker at gunpoint while Bruce is forced to *choose*. Recently, in Hush 2, we see Jason whining about how Clayface impersonated him back in Hush... almost if he *doesn't* know that Clayface once pretended to be him. But he *should* know because he was literally the one who suggested that idea to Hush and doubled down on it by initially pretending he was Hush before swapping with Clayface.. we also know that the current continuity Jason *never* went on a batman style world training. He just trained with a bunch of mystical monks called the all caste. Jason in the post crisis era of UTH didn't have weird mystical blades either so there's that. Bearing that in mind, there's no way Under the Red Hood still happens in the new 52, rebirth or continuity. Or at the very least, a significantly different iteration happened. Lost Days definitely didn't happen, since the time he would have spent in his hypothetical lost days era was 1), not that long compared to the 5-6 years he spent during post crisis and 2), that time was spent with some weird monks prior to him returning to Gotham.

UTRH has been so retconned and changed to hell and back, I'm not even sure the post crisis version of the story is still canon anymore.