Jesus then talks of THIS generation - the generation of the Apostles. He talks of how Jerusalem will be destroyed
And it was destroyed within that generation
Matthew 24 begins as a response to the apostles marveling at the splendor of the Jerusalem temple
Your quotes are the problem - you shouldn't read excerpts. Matthew 24:31 is talking of the tribulation and destruction of the Temple, the world to the 2nd Temple Jews
The drying of the Euphrates - the Romans crossed over the Euphrates on their way to demolish Jerusalem, coming from the east
It was not dried up, and the sounds of musicians is still heard in Jerusalem.