Knowledge about the arrival of Imam Mehdi in Hadith and sunnah?And he will arive I what conditions?

1. APPEARANCE OF IMAAM MAHDI (ALAIHI SALAAM)%0D%0A%0D%0AThe first major sign of the signs of Qiyaamah is the appearance Imaam Mahdi (alaihi salaam). 'Mahdi' is the title to one who guides. According to the dictionary meaning, every Aalim who possesses the correct and true knowledge is called a 'Mahdi', in fact every true and complete Muslim is a 'Mahdi'. However, the Mahdi, who is spoken about in the Ahaadith, is the one who will appear close to Qiyaamah, and it refers to one particular person. He will be from the progeny of Hadhrat Faatimah (radhiAllaahu anha). His name will be Mohammed, his father's name will be Abdullaah and his mother's name will be Aaminah. In external appearance and character, he will resemble Rasulullaah (sallAllaahu alaihi wasallam). He will be a resident of Madinah and will make his appearance in Makkah. The pious people and the Abdaals (Levels in Sainthood) from Shaam and Iraq will take Ba'it (pledge allegiance) at his hands. The "Taaj-e-Kaabah" (Crown of the Kaabah - those, treasures that are buried underneath the Kaabah) will come out and it will be distributed amongst the Muslims. He will first become the king of the Arabs and then of all the Muslims around the world. The world will permeate with justice and peace, just as how its opposites, i.e. oppression and tyranny, had reigned (previously). The Shariah of Muhammad (sallAllaahu alaihi wasallam) will be rejuvenated. During the time of Imaam Mahdi (alaihi salaam), dajjal will make his appearance. It will also be during his reign that Hadhrat Isaa (alaihi salaam) will descend from the heavens onto the eastern minaarat of the Masjid in Damascus, and he will read his Salaah behind Imaam Mahdi (alaihi salaam). Imaam Mahdi (alaihi salaam) will fight the Christians and conquer Constantinople (Istanbul).%0D%0A%0D%0AIMPORTANT NOTE:%0D%0A%0D%0AIt is the firm belief of the Ahlus Sunnat Wal Jamaat that the emergence of Imaam Mahdi close to Qiyaamah is Haqq. It is necessary to bring faith and believe in this. The appearance of Imaam Mahdi (alaihi salaam) is verified in authentic Ahaadith and there is a consensus of opinion of the Ummat on this. With regards the descriptions and explanations of Imaam Mahdi (alaihi salaam), although there are few single reported Ahadith on the matter, this has come down to us right through the ages from the time of the Sahaabah, Taabi'een and all the pious Ulama throughout the east and west in all eras.%0D%0A%0D%0ASheikh Jalaaluddeen Suyuti (rahmatullahi alaih) has written an entire treatise on Imaam Mahdi (alaihi salaam), wherein he has detailed all the Ahaadith and narrations of the Sahaabah regarding Imaam Mahdi (alaihi slaam). The name of this Kitaab is "AI-Arful Wardi Fi Akhbaaril Mahdi". Whoever desires may refer to it. Sheikh Ibn Hajar Makki has also written a treatise on the signs of Imaam Mahdi (alaihi salaam), wherein he has listed up to 200 signs. With all these references and Ahaadith that exist on the signs of Imaam Mahdi (alaihi salaam), it is indeed folly and asinine for anyone to refute the appearance of Imaam Mahdi (alaihi salaam). There are those who have accepted the claim of the (false) claimants to being Imaam Mahdi. May Allaah Ta'ala grant them the guidance of the Straight Path. Aameen.%0D%0A%0D%0ACLAIMANTS TO BEING MAHDI%0D%0A%0D%0AThere were many people who claimed to be the promised Imaam Mahdi, but none measured up to the descriptions given in the Ahaadith, and none will, except the real one that Nabi (sailAllaahu alaihi wasallam) spoke about. They started making all sorts of interpretations and explanations with regard to the real signs of Imaam Mahdi and tried to make them apply to themselves. If making interpretations of the real signs of Imaam Mahdi was the object, then it would be very easy for every person to become a Mahdi. Whoever desires can claim to be a Mahdi, but one must remember that none can be the real Imaam Mahdi (alaihi salaam) that was prophesied in the Ahaadith. If the descriptions given in the Ahaadith regarding the descriptions of Imaam Mahdi is not present in any claimant, then he will never be the prophesied Imaam Mahdi.%0D%0A%0D%0AMirza Ghulaam Ahmed, never had any signs of the prophesied Imaam Mahdi in him. The Mirzaees and Qaadianis were a strange breed believing their leader to be Maseeh and Mahdi. The English were declared as kaafir and dajjaals, yet (according to the Qaadianis) it was haraam to make jihad against them and they also encouraged and regarded as fardh, making du'aa for the continuation of the English rule.%0D%0A%0D%0AO Muslims, what type of Maseeh is this! Hadhrat Isaa (alaihi salaam) will be sent to annihilate dajjaal and not to make du'aa for his continuation and existence.