The Cage might have happened. Pike could have been commanding another ship. This film maintains Trek lore that Pike was the original captain of the Enterprise.
Chekov being 17 does maintain that he was the youngest member of the crew.
I had this very discussion over lunch Saturday.
Enterprise was roughly 20+ years late being christened. Since the point of change was the Kelvin destruction 25 years prior, it's entirely possible that the ship which would have been christened Enterprise was given another name.
Since no background or absolute specifics were given on Spock or Pike, or anything else for that matter in the 25 years between the destruction of the Kelvin, and the launch of the Enterprise, absolutely anything could have occurred, including very similar incidents to the original timeline.
For the mot part, very few planets or incidents would be effected by Kelvin's destruction, other than those which would directly change because of it, such as a Lt. JG. Francois Picard, who was killed aboard the Kelvin and the line of Picard ends there for example.
Talos IV would still exist, and the ship that crashed there would still have occurred since it would have taken place before the Kelvin incident.
And there would be inumerable examples of things that would not have been directly effected by the Kelvin incident.
Many that would have changed, might have only changed superficially. Such as the Cage happening with Pike commanding the USS Defiant, USS Robau or whatever, with Spock as a science officer.
Kirk is STILL the same James T Kirk, his destiny unchanged, but delayed due to circumstances.
The Chekov in the film not being the SAME Pavel Chekov is a very interesting concept. I kinda like that premise.
People who think everything is just being thrown out the window randomly aren't taking the time to think before they type, sorry.