What are the clearest characteristics indicating the truth of one who claims to be the Mahdi?

The Shaykh : Now, we have two clear characteristics of the Mahdi. The first is that he is from the household of the Prophet and the Messenger. The second is that his name is Muhammad ibn 'Abd Allah, and that he must be known by this name from his birth until he reaches the age of accountability and maturity, and the age at which he will take charge of guiding the Ummah to happiness in this world before the Hereafter. Then there is a third characteristic in the first hadith, which we take from the first hadith: . This can actually be interpreted in one of two ways. The first interpretation is that he is not suitable to lead the Ummah; he is zealous in his religion and in his uprightness, but it does not occur to anyone that he is fit to be a leader of the Ummah. So Allah rectifies him in one night, inspiring him to rise to lead the Muslims who gather around him to achieve the dream that Muslims seek today, which is to judge by what Allah has revealed. This is the first interpretation. The other interpretation is that he is a man who is not righteous in himself, living for as many years as Allah wills while being negligent of himself and neglecting some of his religion. So Allah (Mighty and Majestic) inspires him in one night to return to Allah as a repentant and guided person, so Allah rectifies him in one night. This is the third characteristic. The fourth characteristic, which is very important, is that he emerges in Damascus, which was the capital of the land of Sham in the past and Syria in the present, and this is explicitly stated in the authentic hadith. The fifth characteristic is that he meets 'Isa (peace be upon him). They meet in Damascus where: , meaning this Muhammadan Ummah. So when 'Isa descends, he does not descend in the capacity of being a Prophet, because he was a Prophet to the Children of Israel and a Messenger, but rather he comes as a follower of Muhammad (peace and blessings be upon him), as indicated in the famous hadith: , . And this verbal error of mine reminds me of a typographical or written error that occurred in the Tafsir of Ibn Kathir, where this hadith came with the incorrect wording that I mentioned earlier: or it came: . So the mention of 'Isa in this hadith is not correct. The hadith is strong in its aggregate of chains regarding the mention of Musa: . And I found recently, today specifically, I found a narration—for the first time I have come across it—in the Musnad of Ishaq ibn Rahawayh, of which a copy of the fourth volume is available in microfilm at the Islamic University Library. I found the hadith with a strange wording: . The point is that when 'Isa descends and the prayer has been established for the Mahdi, and the Mahdi presents him to lead the people, he refuses and says to him: No, you go ahead and lead them, as an honor from Allah for this Ummah.