Lets take a look one step at a time at all the differences between each timeline and how they are explained in official resources. The Prime Reality(abbreviated as PR) is the known Star Trek galaxy created by Gene Roddenberry, and the Alternate Reality( aka AR) is the “new” reality that was created by J.J. Abrams. It is officially stated that the two realities continue to exist separately.
2233- In the PR Kirk was said to be born on earth in Iowa.
In the AR this idea was thrown out and replaced with Kirk being born in space. Also in this timeline Kirks father was killed with the apperance of the black hole and Nero. This serves as the “fork” that separates the two realities.
note- In the prime reality The Enterprise logo did not become the official Starfleet logo until Kirk finished his historic 5 year mission. In the alternate reality before the Enterprise, the Kelvin had the known “spearhead” logo and became the logo of Starfleet in memory of the Kelvin after its destruction.
note- Scans taken of the future Romulan vessel, the Narada, by the Kelvin were brought back by the survivors and their shuttles. This study led to many major technological advances which places Starfleet way ahead of its time. These advances lead to the new styled communicators, phasers, and overall ship design. If you compare the early phasers and communicators aboard the Kelvin to TOS you will notice they are very close.
2241- AR-Due to the “change” Pavel Chekov is born now, while in the PR Chekov wasnt born till 2245.
2245- PR- The Enterprise is launched on its first 5 year mission under Cpt. April.
AR- As a result of the new technological advances, due to the Narada studies, the Enterprise project gets put on “hold” for over a decade. The Constitution class Ship is redesigned much larger than the original plan as seen in the PR Enterprise. This new advancement includes using Dilithium for the warp reactors, as are the other Starfleet vessels. The end result is a bigger better fleet for the federation.
note- dilithium in the PR wasnt used until mid 2260’s
note- the PR Enterprise was 305meters, the AR Enterprise 725meters. The size difference is also explained by the “technological Advancement” which is why the bridge is bigger and more sleek.
2250- PR- Kirk enrolls in Starfleet, and serves on the USS Republic as a cadet. AR- without Kirks father figure James T. Kirk had no interest in joining Starfleet. As a result Kirk did not join starfleet until 2255.
2254- AR- Spock is promoted to Commander, which is earlier than in the PR(no actual date is given).
PR- Kirk graduates beating the Kobayashi Maru, in the AR Kirk doesnt beat the Kobayashi senario until 2258.
2255- AR-Kirk enlists in Starfleet (refer to 2250)
2258- PR at this time Pike would be making his second 5 year mission on the Enterprise.
AR- Enterprise is launched!!! Narada reappears, destroys vulcan. The incident results in Kirk defeating Nero and jumping up to Captain of the Enterprise which is six years earlier than the PR. ( In PR Kirk and his crew do not start their mission on the Enterprise until 2264. In addition Vulcan was never destroyed)
note- The destruction of Vulcan led to the death of Spocks mother, whom in the PR lived on to old age helping him with his human side. AR- with the death of Spocks Mother, Spock and Uhura become closer and intimate.
Alternate Reality equipment (with the Narada advances)-