MINA OR MEENA
Mina, is a place which lies between the City of Makkah and Muzdalifah in Saudi Arabia, is now known as tent city. Here are the white pillars representing the devil at which the hajj pilgrims cast the pebbles when they gathered at Muzdalifah. 
On the first official day of the pilgrimage, the millions of pilgrims that have now gathered travel from Makkah to Mina, a small village east of the city. There they spend the day and night in enormous tent cities, praying, reading the Qur’aan, and resting for the next day.
Day of Tarwiah means 8th day of Zilhijjah and also the first day of Hajj. A pilgrim performing Hajj AlTamatt'u should intend Ihram, from the place where he is staying, on the 8th day of Zilhijjah, which is the Tarwiah Day, and leave to Mina in the morning. In Mina, the pilgrims pray Dhuhr, Asr, Maghrib and Isha of the 8th day of Zilhijjah and Fajr of the 9th day of Zilhijjah. The pilgrim remains in Mina until sunrise of the 9th day of Zilhijjah and then leaves to Arafah. On the 10th day early morning pilgrim must come to Mina before sunrise. 
Staying overnight in Mina on the night before the eleventh and twelfth of Zilhijjah is obligatory according to the majority of scholars, and the one who fails to do it without an excuse has to offer a sacrifice of a sheep, to be slaughtered in Makkah and its meat distributed to the poor of the city.
If a person cannot find any room in Mina, he should stay where the tents end, even if it is in Muzdalifah, because Allah (Glory be to Him) says (interpretation of the meaning): “So keep your duty to Allah and fear Him as much as you can” Qur’an.Surah Taghaabun 64:16
Staying overnight in Mina during the days of Tashreeq is obligatory according to the majority of scholars one should stay there for most of the night. And not staying overnight in Mina during the Days of Tashreeq due to one of the following cases:
The first case: when a person does not stay overnight in Mina because he has an excuse.
Shaykh Ibn Baaz (May Allah have mercy on Him) was asked about the ruling on a person who does not stay overnight in Mina during the Days of Tashreeq. He said: “He is not obliged to offer any sacrifice because Allah says (interpretation of the meaning): ‘So keep your duty to Allah and fear Him as much as you can’ [Qur’an.Surah Taghaabun 64:16] – whether he did not stay overnight at Mina because of sickness or because there was no room, of for some similar legitimate excuse such as those who bring water to the pilgrims and those who tend sheep, and whatever else comes under the same rulings.
The second case: when a person does not stay overnight (in Mina) during the days of Tahsreeq with no excuse. The Shaykh (may Allah have mercy on him) said: Whoever does not stay overnight in Mina during the Days of Tashreeq with no excuse has failed to do something which was prescribed by the Messenger of Allah (May Allah honour Him and grant Him peace) in both word and deed, and by the fact that he made a concession for some of those who have excuses such as shepherds and those who bring water to the pilgrims. Concessions can only be made when there is something which has to be done. Hence staying overnight in Mina during the Days of Tashreeq is considered to be one of the obligatory duties of Hajj, according to the more correct of the two scholarly views, and whoever does not do that and has no legitimate excuse has to offer a sacrifice, because it was reported that Ibn ‘Abbas (R) said: “Whoever fails to do one of the rituals [of Hajj] or forgets it, let him offer a sacrifice.” It is sufficient to offer one sacrifice for not staying overnight in Mina during the days of Tashreeq.” Majmoo’ Fataawa al-Shaykh Ibn Baaz Vol. 5
He should offer the sacrifice and share out its meat among the poor in the Haram, and he should not eat any of it.
Ruling on Going out of Mina by day and coming back at night during the days of al-Tashreeq and the Obligation of staying in Mina
The sunnah is for the pilgrim to stay in Mina throughout the day, following the example of the Prophet Muhammad (May Allah honour Him and grant Him peace), who did not leave Mina except to do Tawaaf al-Ifaadah. And he must stay in Mina for most of the night. There is no sin on him if he departs from Mina during the day to go to Makkah or elsewhere, especially if that is because there is no place to stay.
Shaykh Ibn Baaz (May Allah have mercy on him) was asked: A person moved on from ‘Arafat then he stoned the first Jamarah, then he did tawaaf and saa’i, then he stayed in his place in Makkah until ‘Asr, then he went back to Mina and slaughtered his sacrificial animal. Does he have to do anything for this?
There is no sin on him for that. Whoever stays in Makkah during the day of Eid or during the days of al-Tashreeq in his house or with his companions, there is no sin on him for that. But it is better to stay in Mina if possible, following the example of the Prophet Muhammad (May Allah honour Him and grant Him peace) and his companions (may Allah be pleased with them). If it is not easy for him to do that and it is too difficult for him, and he enters Makkah and stays there during the day, then comes back to Mina at night, and stays there overnight, there is nothing wrong with that, from Majmoo’ Fataawa al-Shaykh Ibn Baaz (17/365).
Shaykh Ibn ‘Uthaymeen (May Allah have mercy on him) was asked about some of the pilgrims who live in al-Azeeziyyah and stay in their homes during the days of al-Tashreeq.
He replied: What I think is that those who live in al-Azeeziyyah should not stay in their homes during the day. Undoubtedly it is Sunnah to stay in the tents in Mina, because Hajj is a kind of jihad for the sake of Allah (Glory be to Him), as the Messenger (May Allah honour Him and grant Him peace) said to ‘Aa’isha (R), when she said: “Is there any jihad for women?” He said: “Yes, a jihad in which there is no fighting: Hajj and ‘Umrah.” So what is prescribed for the pilgrim is to stay in Mina by night and by day.
He (may Allaah have mercy on him) was also asked: Does going out during the days of al-Tashreeq to places that are close to Makkah, such as Jeddah, affect the Hajj?
He (may Allaah have mercy on him) replied: It does not affect the Hajj, but it is better to stay in Mina by night and by day, as the Prophet Muhammad (May Allah honour Him and grant Him peace) did, Majmoo’ Fataawa al-Shaykh Ibn ‘Uthaymeen (23/241, 242)
The guideline on staying in Mina is that the pilgrim should spend more than half the night there. The hours of the night are counted from when the sun sets until when the dawn breaks. Based on this, you should work out the time from sunset until dawn, according to the hours in Mina. If you spent six hours in Mina, this is more than half of the night, so you have done what was required.
Shaykh Ibn ‘Uthaymeen (May Allah have mercy on him) was asked: What is the length of time that the pilgrim must stay in Makkah during the days of al-Tashreeq?
He replied: The scholars (May Allah have mercy on them) said that staying overnight in Mina must be for most of the night. If we assume that the night is ten hours long, then five and a half hours may be spent in Mina and whatever is more than that is Sunnah, Fataawa al-Shaykh Ibn ‘Uthaymeen (23/244).
And the pilgrim during the Days of Mina must take care to pray the five daily prayers with the congregation - and it is best to pray the Masjid of Khaif if he is able to, as the Prophet Muhammad (May Allah honour Him and grant Him peace) said: Seventy Prophets have prayed in the Masjid of Khaif.