What are the conditions of witr prayer and is it permissible to offer it in three rak'as with one tashahud?

The witr prayer [the final prayer at night] is a confirmed Sunnah and has the same conditions for voluntary prayer. It does not have a set manner of performance and its reward varies accordingly.

The first manner
This is optimal manner and comprises separating each pair of rak’as [cycles of prayer] with a tashahud [testification of faith] and salam [greeting closing the prayer]. This manner is better than joining the rak’as based on the hadith narrated by Aisha who said: “The Prophet (peace and blessings be upon him) used to pray, after night and before dawn prayers, eleven rak'as where he made salams after every pair, and prayed the eleventh rak’a as witr” [recorded by Bukhari and Muslim].

The second manner
It comprises joining all rak'as and ending them with a final tashahud.

The third manner
This is the least in reward and comprises joining the rak’as and reciting two tashahuds to differentiate it from the sunset prayer due to the hadith: “Do not offer the witr prayer like the sunset prayer”[recorded by Al-Daraqutni who declared it sound]. It is written in the book Umdat Al-Salik that the minimal performance of witr is one rak’a and the maximum performance is eleven, finishing with salam after every pair. However, the minimum of the complete witr is three rak’as with two salams … a person is free to perform three and eleven rak’as with one salam. It is also permissible to offer the tashahud after the tenth and eleventh rak’as. To recite two tashahuds is superior as more than this renders the prayer null and void.
Accordingly, it is permissible for the inquirer to offer witr prayer in three rak’as with a single tashahud.
And God the Almighty knows best.