The last question is more accurately translated "and of the end of the age". The "age" in question was the Old Covenant age. The disciples had just talked about how magnificent the Temple was, and Jesus dropped a bombshell on them by telling them it would be destroyed. To them, this was huge, almost unbelievable. Thus, they asked Him those questions. Especially in Luke's account of the Olivet Discourse, Jesus provided a very specific sign - "when you see Jerusalem surrounded by armies, you know its desolation is near". It's not that Jesus literally came in AD 70, but He figuratively "came" in judgment upon Israel. His literal Second Coming may still be 1,000 years in our future, or it could be tomorrow.
No, Jesus didn't have to teach them past history. However, He did quote from Daniel's prophecy in teaching them about the events that would culminate in Jerusalem's destruction. That prophecy fit perfectly with the Jewish Wars of AD 66-70.
So, since you believe He was referring to a future sign of His return, what do you think this "sign" will be? I'm sure it's connected to your "fig tree" view. Many Christians believe the "fig tree" refers to May 14, 1948, when Israel became a nation again. Is this what you are getting at?
The end of the age was the Cross. The next age would end at the Second Coming. There was no age that ended in 70AD. 70AD was not the birth of the NT age.
There is no overlap in ages if that is your point. There is only one sign of the Second Coming. That is the sign of Jesus actually in the air at the Second Coming.
The generation that sees the fig tree blooming will see all things mentioned in Matthew 24. But the fig tree is not a sign. The GT is not a sign. The AoD is not a sign. Jesus said the only sign (at least as Matthew recorded the OD) is the actual return. Those who see the actual sign will either be prepared or not. Like the 10 virgins. Some will be prepared. Some will not be prepared.
No, the fig tree is not a sign unless one calls it one. Jesus did say that generation would see everything, but obviously not all of that generation. Only some would be around to see it all. Life expectancy is higher than in the first century. 40 years is too short to kill off that generation by today's standards of living. Obviously
40 reasons why 1988 was the year was not correct. 40 years was not relative in the first century just like it is not relative today. But certainly 40 years after the Cross was plenty of time to kill several generations. As those who crucified Jesus did say they and their offspring for several generations would pay the price. I doubt that day they thought all of Israel would be destroyed and dispersed throughout the empire.
But to claim the whole NT was only good until 70AD is missing the whole point of the Cross and the NT. While Jesus was addressing His people, the NT and Revelation would apply to the church and the end of the NT age. Which has not ended, yet. The Second Coming is to restore Israel. It is also the moment the NT church age ends. 70AD did not restore Israel nor end the Church age. It is wrong of Preterist to claim otherwise, just like 1988 literally had no meaning whatsoever.
In Luke there is no sign mentioned. Jesus gives a list of events that would happen. In fact Luke does not even separate the OD from what Jesus said in the temple. Luke 21 is more relatable to 70AD than Matthew is because Luke mentions armies not the AoD. The argument is not about Jerusalem and the temple being destroyed. The argument is about the Second Coming and an age ending. Some want to spiritualize 70AD. It was not the Second Coming nor end of an age. It was not even a spiritual event. It was about carnal rebellious Israel who tried to revolt against more carnal wicked humans. These carnal offspring of those who wanted Jesus dead were reaping the rewards they claimed upon themselves for shedding innocent blood.
The whole point is that applying what was meant for physical Israel to that which applies to the spiritual church will not work. Knowing the difference is having wisdom, being spiritually discerned, and rightly dividing the Word of God.