There are some Hadiths in Sahih Muslim which mentions that the Qunut is Sunnah? Do we have to do it for every prayer?

Praise be to Allah, the Lord of the World; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

As a rule, al-Qunut is Sunnah in al-Witr prayer. This is the opinion of Imam Ahmad and others. It is better to make al-Qunut before Ruku', although it is acceptable to be after Ruku'.
Humaid reported that when Anas was asked about al-Qunut in al-Fajr (morning) prayer said: "We were used to making al-Qunut before and after Ruku'" . [ Ibn Majah ].
As for al-Qunut in al-Fajr prayer, there is disagreement among Muslim scholars concerning this issue.
Imams Ahmad and Abu Hanifa (May Allah's Mercy be upon them both) believe that it is not a Sunnah to make al-Qunut in al-Fajr prayer or any other prayer except al-Witr.
Muslim reported that "Allah's Messenger (Sallallahu Alaihi wa Sallam) make al-Qunut for one month praying against an Arab tribe, and then, he stopped" .
Abu Malik said to his father: 'You prayed with Allah's Messenger (Sallallahu Alaihi wa Sallam), Abu Bakr , 'Umar , Uthman and with 'Ali here in Kufa for five years. Did they make al-Qunut in al-Fajr?' His father replied: 'O my son! Are you an innovator?' Reported by al-Tirmizi and said: 'It is a good and sound Hadith'. Most scholars follow such a rule.
Imams Malik and al-Shafi'e believe that it is a Sunnah to make al-Qunut in al-Fajr prayer at all times.
Anas said: "Allah's Messenger (Sallallahu Alaihi wa Sallam) was used to making al-Qunut in al-Fajr prayer Till breathed his last". [Reported by Ahmad ].
'Umar was used to al-Qunut in the presence of the Prophet's (Sallallahu Alaihi wa Sallam) companions and others.
Here, we state that such a difference in opinion must be respected. In addition, it is a Sunnah to make Sujud al-Sahoo (forgetful prostration) for one who does not make al-Qunut according to Imam al-Shafi'e .
Allah knows best.