The alternate ending for Terminator 2: Judgment Day, available on the Ultimate Edition DVD and the Skynet Edition Blu-ray, shows Sarah alive and well 30 years after the primary events of the film. She is an elderly grandmother and John is a Senator in a world in which Skynet was never able to start its war on humanity.
Alex is the physical embodiment of Skynet, housed in a T-5000 Terminator. From an unknown alternate timeline, it infiltrates the Tech-Com unit commanded by John Connor, who leads the Resistance. Near the end of war in an unknown alternate future, Skynet developed the T-3000, a human turned into a Machine-Phase Matter Terminator. It later uploaded itself into a T-5000 Terminator and travelled

The early parts of "Terminator Genius" play out like a prologue for the original movie. John Connor and Kyle Reese are shown making a final assault on Skynet in the year 2029 with the Human

Happy belated anniversary of Judgment Day, everyone! August 29th, 1997 was the day that Skynet became self-aware and ended the world, according to 1991’s Terminator 2: Judgment Day. Or at lea… Skynet is not "evil" in the conventional sense of the word. It was built for a purpose, and it fulfilled that purpose; even if it was in a roundabout way that destroyed the world in order to achieve its goal. It simply used the resources it had available--the strategic defense assets of the United States.
It's a bit complicated.. The rumour among the human rebels in Terminator: Salvation is that the Terminator's skin is taken from living humans. This is backed up by the fact that we see an industrial-scale dissection chamber (with multiple beds) later in the film, however these appear disused which would lend weight to the theory that Skynet has developed the ability to grow skin artificially:
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how did skynet survive terminator 2