Bismihi ta'ala

Wa alaikumussalam

1) According to the principles of Hanafi Jurisprudence, Hadith of Rasoolullah Salallahu alaihi wasallam is ranked as the second source of Islamic Law. Ijma' (consensus) is third in line.

2) There is a difference of opinion regarding this amongst the Hanafi Jurists. The majority view is, Ijma can only be established when all of the Jurists of that era unanimously decide upon something, even the disagreement of one or a minority would not allow an Ijma' to take place.

However, some of the Jurists such as Sarakhsi are of the opinion that even the agreement of Three Jurists constitutes an Ijma'. Some say 2. Some even say that if there only remained one Mujtahid alive, then his opinion alone would be considered Ijma', due to the fat that at the time of isolation the term 'ummah' is befitting for him.

3) Can an Ijma' outweigh a Hadith? FIrstly, it is unthinkable that the Sahaabah would unanimously contradict a Hadith that is Mutawaatir. There are many terminologies, principles and concepts one must understand before tackling this question. This requires alot of depth.

And Allah knows best.