Is There Tarawih the Night before Ramadan?
Question

When should we start to pray Tarawih prayer, on the night of the first day of Ramadan (when the moon is sighted or the previous month is completed) or after ‘Isha prayer on the first day of Ramadan?
Praise be to Allah.When does tarawih start?
It is prescribed for the Muslim to perform Tarawih prayer after ‘Isha on the first night of Ramadan, which is the night on which the new moon is sighted or the Muslims complete thirty days of Sha`ban. 
When does tarawih end?
Similarly at the end of Ramadan, Tarawih prayer should not be offered if it is proven that the month has ended, either by sighting of the new moon of ‘Eid or if the month of thirty days has been completed. 
It is clear that Tarawih prayer is not connected to the fast during the day in Ramadan, rather it is connected to the onset of the month at night in the beginning, and the last day of Ramadan at the end. 
Is tarawih compulsory?
We should not say that Taraweeh prayer is a nafl prayer and it is permissible to offer it on any night and in congregation, because Tarawih prayer is limited to the month of Ramadan, and those who offer this prayer are seeking the reward that comes for praying it. 
Should tarawih be offered in congregation?
The ruling on offering this prayer in congregation is different from the ruling on offering other prayers in congregation. In Ramadan, it is permissible to pray Tarawih in congregation on each night, whilst announcing it and encouraging others to join, unlike qiyam at other times, where praying qiyam in congregation is not part of the Sunnah unless it is done without having the intention beforehand, or it is done for the purpose of encouraging and teaching others.  So it is Sunnah to do it sometimes without committing to doing it all the time or persisting in that. 
Can you pray tarawih outside of Ramadan?
Shaykh Muhammad al-Salih al-‘Uthaymin (may Allah have mercy on him) said: 
“Tarawih at times other than Ramadan is an innovation (bid’ah). For example, if the people wanted to gather to pray qiyam in congregation in the mosque at times other than Ramadan, this would be an innovation. 
There is nothing wrong with a person praying in congregation in his house occasionally at times other than Ramadan, because this is what the Prophet (peace and blessings of Allaah be upon him) did. Once he led Ibn ‘Abbas, and once Ibn Mas’ud and once Hudhayfah ibn al-Yaman, in prayer in his house, but he did not adopt that as a regular Sunnah and he did not do that in the mosque.” (Al-Sharh al-Mumti’, 4/60, 61) 
Based on this, whoever offers Tarawih prayers before it is proven that Ramadan has begun is like one who offers a prayer at the wrong time. No reward will be written for him, even if he is free of the sin of doing that deliberately. 
And Allah knows best.