Did Prophet Muhammad authorised his Sunna?

It has been claimed that during the ‘Farewell Sermon’, which prophet Muhammad delivered shortly before his death, he told his people that he leaves for them two things which if they follow they would never be misguided. The first being the book of God and the second being his Sunna.
The hadith followers justify the legality of following the hadith mainly on the strength of this hadith. They argue that unless they follow the hadith they would not be able to follow the Sunna of Muhammad?
What many people do not know is that there are three versions of this one hadith. The three versions are:

1- First version (upheld by the Shia Muslims):
The Messenger of Allah said, "I left for you what if you hold on to, you will never be misguided, the book of Allah and ‘itrati’ (my family).” (Moslim 44/4, Nu2408; Ibn Hanbal 4/366; darimi 23/1, nu 3319).

2- Second version (upheld by the Sunni Muslims):
The Messenger of Allah said, "I left for you what if you hold on to, you will never be misguided, the book of Allah and my Sunna." (Muwatta, 46/3).

3- Third version (ignored by Sunni’s and Shia):
The Messenger of Allah said, "I left for you what if you hold on to, you will never be misguided, the book of Allah." (Moslim 15/19, nu 1218; Ibn Majah 25/84, Abu dawud 11/56).

This third version is the version hated by the Sunni and Shiite Muslims alike. This is the only version which conforms with the Quranic words which state that Muhammad's only duty was to deliver the Quran (5:99). Many Sunni Muslims and Shiite Muslims do not even know that this version of the sermon exists. In reality, they do not want to know, the truth hurts!
The same people who uphold the hadith are aware of a hadith which they regard as ‘sahih’ (authentic) and which confirms that the third version above is the only truthful version. The hadith says:

The messenger of Allah said, "Do not write anything from me except Quran. Anyone who wrote anything other than the Quran shall erase it."
(Ahmed, Vol. 1, Page 171, and Sahih Moslim, Zuhd, Book 42, Number 7147).

The immediate question that comes to mind after reading the hadith above is:
If the Prophet commanded his people not to write his hadith, how would he expect them to follow his Sunna after he is dead? That is, if he did in fact instruct them to follow his Sunna at all!

In any case, the genuine believers do not need the verdict one of hadith or another, they are satisfied with the Quranic words:

1- We read in the Quran that the Sunna of God is the only sunna:

"Such was the sunna of God for those who have passed on before. You will find that
there is no substitute for the sunna of God."33:62

2- In all the Quran, there is no reference or mention of a Sunna for Muhammad.

Related Subjects:

- Dozen reasons to follow the Quran alone

- History of hadith

- How authentic is the hadith?