What is the ruling on the prayer of one who missed one or more rak'ahs of the prayer and left the final tashahhud with the imam, on the pretext that this rak'ah is his first and not his last?

If a latecomer joins the Imam in the last rak'ah or before, he is not obligated to recite the tashahhud with the Imam. Rather, he must sit in 따라 Imam. It is better for him to concur with the Imam in the tashahhud. If the tashahhud was obligatory upon him, then he must perform it. If he intentionally omits it, his prayer becomes invalid according to the Hanbalis. However, the questioner's prayer is valid because what he did was contrary to what is better, not what is obligatory.