The ruling on a latecomer delaying the first tashahhud from its place

Question:
A man prayed with the imam and caught the last rak'ah of the 'Asr prayer. After the imam finished the prayer, he stood up to complete his prayer, but he sat down for the first tashahhud after the third rak'ah. What is the ruling on his prayer?

Answer:
His prayer is valid, but the tashahhud that he delayed from its place is obligatory to be performed by sitting after the second rak'ah, after the salam. If he stands up and reaches the second rak'ah after the salam, he sits, then stands up and performs the rak'ah in the place of the tashahhud. So he moved it from its place and placed it after three rak'ahs, which is not its place. This means he left the first tashahhud. If he remembers, whether he remembers while in the prayer or shortly after the prayer, he prostrates two prostrations for forgetfulness. If a long time has passed, his prayer is valid and the prostration for forgetfulness is dropped from him due to the forgetting. Yes.