...in one core universe. Otherwise it all could be ridiculously confusing unreasonably so. If the attacker skynet was a hundred years in the future picking a time to change his awakening and entering the temporal field of terminator 2 timeline but in 1973 and 1984 and 2017 but different from the Canon because of the alterations from 1973 on. We can still have alternative characters trying to stop Sara and kyle... Fighting themselves... John Connor said it in Genysis that time doesn't erase the time traveler... Obviously because John isn't even born now I'm 2017. So plenty of roads to take the characters on and can include all four films in the Canon... Pretty much from terminator to salvation has to occur before the events of Genysis occur. I mean it's like if you could start terminator from 1984 with a stop watch to when sunny goes back to attack. Making other universes presents the problem of why this one... What makes it so special.... Too much is needed to make that make sense...but if skynet who attacks John is from a few decades after salvation and he goes into one of the three time bubbles that exist outside of space time ie terminator 1984 is number 1 and bubble number two is terminator judgement day and bubble number three is rise of the machines.... These bubbles exist when the time machine is activated. And it was three times in different timelines....so the kyle from salvation and the kyle from judgement day would have lived semi different lives. Hence the differences in how kyle met John. And one bubble already existed for Sara to know kyle dies... So bubble number 2... Just before the events of judgment day changing the course of the future and making those events not occur anymore... And riveting semi back to timeline 1 the one that has never been seen before... The one where kyle is NOT John dad and judgment day happened later on it was moved up when the tech was discovered by cyberdyne.