Signs of the Judgement Day in Order
Question

In the present distressed situation many people including scholars are found to talk about the Renaissance of Islam and the emergence of Imam Mahdi. Who is or may be Imam Mahdi and is there any evidence about his possible emergence, in the light of Quran and Hadith? 
What will be the order of occurrence of events before the Qiyamah, including the emergence of Imam al-Mahdi, Fitna-ad-Dajjal, Yajuj Majuj and ‘Isa (Jesus)? Kindly reply in detail
Praise be to Allah.Who is Imam al-Mahdi?
Imam al-Mahdi will be a righteous man from among the descendants of the Prophet Muhammad (peace and blessings of Allah be upon him), who will appear at the end of time, through whom Allah will set mankind’s affairs straight, and will fill the earth with fairness and justice just as it was filled with wrongdoing and oppression. 
What is the name of Imam al-Mahdi?
The name of Imam al-Mahdi will be the same as the name of the Prophet (peace and blessings of Allah be upon him), and his father’s name will be the same as that of the father of the Prophet (peace and blessings of Allah be upon him). 
So his name will be Muhammad ibn ‘Abd-Allah al-Mahdi, or Ahmad ibn ‘Abd-Allah al-Mahdi. He will be descended from Fatimah the daughter of the Messenger of Allah (peace and blessings of Allah be upon him), through al-Hasan ibn ‘Ali (may Allah be pleased with him). 
Signs of the coming of Imam al-Mahdi
The sign of his appearance will be widespread corruption and the earth being filled with wrongdoing and aggression. 
There are a number of ahadith which point to his appearance and attributes being as described above. When taken together these reports reach the level of tawatur (i.e., narrated from so many people by so many people that it is inconceivable that they could all have agreed upon a lie). This is explained in more detail in question no. 1252 . 
References
Al-Mahdi al-Muntazar by Dr. ‘Abd al-‘Alim al-Bastawi, 1/256; 
Ashrat al-Sa’ah by Yusuf al-Wabil, p. 249. 
Order of the Signs of the Judgement Day 
With regard to the order in which the portents of the Hour will appear, there is some difference of opinion among the scholars, the reason being that no such order of events is narrated in the Sunnah. However the scholars have determined the order of some of the events, as follows:
Appearance of the minor signs of the Hour 
1 – The appearance of the minor portents of the Hour, of which there are many which will not appear in any specific order. These include: 

the sending of the Prophet (peace and blessings of Allah be upon him) and his death; 
the plague of ‘Amwas; 
the appearance of tribulations;
the loss of honesty; 
the disappearance of knowledge; 
the spread of riba, 
musical instruments and alcohol; regarding these things as permissible; 
competition in erecting tall buildings; 
a great deal of killing; 
time passing more quickly; 
adornment of the mosques; 
prevalence of shirk; 
the spread of immorality; 
a great deal of stinginess; 
many earthquakes; 
landslides, 
transformations and pelting with stones from the heavens; 
disappearance of righteous people; 
believers’ dreams coming true; 
neglect of the Sunnah; 
a great deal of lying; 
a great deal of false testimony; 
a great deal of sudden death; 
a great deal of rain but little growth of vegetation; 
wishing for death; 
increase in numbers of the “Romans” and fighting them; 
and other signs which are narrated in sahih ahadith from the Prophet (peace and blessings of Allah be upon him). 

Appearance of al-Mahdi
2 – The appearance of the Mahdi , who will appear before the Dajjal and before the descent of ‘Isa ibn Maryam (peace and blessings of Allah be upon him). This is indicated by the hadith of Jabir (may Allah be pleased with him) who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: “ ‘Isa ibn Maryam will come down and their leader the Mahdi will say to him: ‘Come and lead us in prayer.’ But he will say: ‘No, one of them should lead the others in prayer, as a sign of honour from Allah to this ummah.’: Narrated by al-Harith ibn Abi Usamah in his Musnad. 
And Ibn al-Qayyim said in al-Manar al-Munif (1/147): its isnad is jayyid. The hadeeth is narrated with a mawsul isnad in Sahih Muslim, without naming their leader. Muslim’s report says: “… ‘And ‘Isa ibn Maryam (peace and blessings of Allah be upon him) will come down and their leader will say to him: ‘Come and lead us in prayer.’ But he will say: ‘No, one of them should lead the others in prayer, as a sign of honour from Allah to this ummah.’” Narrated by Muslim, 225. 
So ‘Isa (peace be upon him) will follow the Mahdi in prayer, which indicates that the Mahdi will appear before ‘Isa, and ‘Isa will kill the Dajjal, which indicates that the Dajjal will appear during the time of the Mahdi. 
Appearance of al-Dajjal
3 – The appearance of the Dajjal – for more detail about his emergence, please see Questions no. 171 , 8301 . 
The descent of Jesus
4 – The descent of ‘Isa ibn Maryam and his killing the Dajjal. 
5 – The appearance of Yajuj and Majuj (Gog and Magog). One indication that Yajuj and Majuj will emerge at the time of ‘Isa (peace be upon him) is the hadith of al-Nawwas ibn Sam'an, which says that the Prophet (peace and blessings of Allah be upon him) told them about the Dajjal, and said: “Whilst he is like that, Allah will reveal to ‘Isa: ‘I have released slaves of Mine whom no one will be able to fight. Take My slaves to safety in al-Tur (Sinai),’ and Allah will send Yajuj and Majuj , who will come swarming down from every mound. The first of them will pass by Lake Tiberias and will drink the water in it, and the last of them will pass by it and will say, ‘There was water here once.’” Narrated by Muslim, no. 2937.  
Then the signs will come quickly, one after another. According to a hadith of Abu Hurayrah (may Allah be pleased with him), the Prophet (peace and blessings of Allah be upon him) said: “The signs will come one after another, like beads falling from a string”. Narrated by al-Tabarani in al-Mu’jam al-Awsat; classed as sahih by al-Albani in Sahih al-Jami’. Then the sun will rise from the west, the Beast will emerge, and there will be landslides and other major signs.  We ask Allah to make us steadfast unto death.
And Allah knows best.