There are any official info?
Not really. In "The Menagerie," all Kirk said was that he briefly met Pike when he assumed command of the Enterprise. That Pike is now something of Kirk's mentor in the film would seem to be a change in and of itself.
True. And TOS said nothing about the precise circumstances of why Kirk was chosen, although non-canon softcover novels have tackled the issue over the years with different theories. We know the Mirror Kirk assassinated HIS Christopher Pike to take over the ISS Enterprise. But that's all.
lol - Now that isn't going to happen - but I bet this would keep the purists happy - half way through the film, Pike gets shot in the back by Kirk, who says "it was a romulean, he went that way!" - we then realise this timeline is totally broken and at the end Kirk realises how awful his life is, he travels further back in time further and dies saving his mother and father.
The original timeline snaps back and the amazing twist, is that it's all being a complete headfuck by Abrhams who's actually a hardcore canon purist. We see then a Cgi'd young william shatner going off to attend Star Fleet academy.