Does one who is late for the prayer raise his hands when he stands from the first Tashahhud in his first rak'ah of the prayer, or does he raise his hands in the rak'ahs that coincide with the imam's standing from the second rak'ah?

What the latecomer (masbuq) does, raising his hands when the Imam stands up from the first tashahhud, is correct and legislated. In fact, he raises his hands even if the Imam does not, because the reason for raising the hands when standing for the third rak'ah is the rising from the tashahhud, and this meaning is present for the latecomer.