What is the ruling on supererogatory prayers in Ramadan, and what is the prescribed number of rak'ahs for Tarawih prayer? Is there any evidence for praying 30 rak'ahs for Tarawih?

Voluntary prayers and the night vigil during Ramadan (Qiyam Ramadan) are supererogatory acts, as the Prophet, peace and blessings be upon him, encouraged them by saying: "Whoever observes night prayer in Ramadan out of sincere faith and hoping for a reward from Allah, all his past sins will be forgiven." The Prophet, peace and blessings be upon him, did not specify the number of rak'ahs for Qiyam Al-Layl or Tarawih. It has been narrated that he prayed eleven rak'ahs, and perhaps thirteen. The night prayer is performed two rak'ahs at a time, and the matter is flexible; there is no harm in increasing or decreasing from a specific number. Jurists have differed on the number of rak'ahs, but the correct view is that all of this is good. Increasing or decreasing the number of rak'ahs depends on the length or shortness of the standing (qiyam).