You are making a simple comprehensible verse into a complicate one just for a reason to suit your tenet . Taking your translation ( which is not different than mine though) :
Say* [O, Mohammad], "If I** strayed, I** would only stray against myself***. But if I** am guided, it is by what my Lord reveals to me**. Indeed, He is Hearing and near." "
* Addressed to Muhammad ( you mentioned already)
** Who is that 'I/me/myself' .? It was Prophet Muhammad .
So what is the big deal ? It was Prophet Muhammad who would go astray for his own short-comings and would be fallible only when Almighty GOD would reveal Wahi to him .Moreover I backed this true understating of the verse with the example of Qur'an that chapter 66 depicted how Prophet Muhammad did wrong with his own decision and that Almighty ALLAH rectified himwith the wahi of 66:1-5 . It makes a perfect sense , obviously for an honest reader of the book of ALLAH .
53:1-4 " By the star when it plunges,«1» your companion is neither astray, neither errs,(according to what he says/ his Religion)«2»nor does he speak out of desire.«3» Indeed it is not except a Revelation which is revealed,«4» ".
This verses interpret 34:50. So 34:50 never means that Prophet Mohammad went astray for his own short-comings! This verses and 34:50 say that polytheists were saying that, Mohammad has gone astray according to his religion, and Allah replied them that your companion is neither astray, neither errs,(according to what he says, i.e. his Religion).
So I didn't make a simple comprehensible verse into a complicate one just for a reason to suit my tenet! I just consider all verses of Qur'an and then translate a verse.
Where this 'Hadith' came from ? The verse remotely not relating Hadith in the context of the verse . It simply says ' teaching them the book ' . The book is Qur'an , which Prophet Muhammad was teaching them , Not 15,000 Ahadith of Al-Kafi , as you mistakenly perceived .
A scenario , imaginary of course , for your perusal ( assume Prophet Muhammad was teaching the book to Imam Ali) :
Imam Ali : Ya Prophet, Who is our GOD ?
Prophet : Ya Ali , verse x:x says ' ALLAH is your only GOD ' .
Imam Ali : Ya Prophet , has ALLAH a son ?
Prophet : Ya Ali, verse y:y says ' ALLAH does not beget nor is begotten' .
Imam Ali : Ya Prophet , What is the name of our religion ?
Prophet Ali : Ya Ali , verse z:z says , ' Islam is your religion' .
Hopefully you get this simple fact .
1. 5:38 " [As for] the thief, the male and the female, amputate their hands in recompense for what they committed as a deterrent [punishment] from Allah. And Allah is Exalted in Might and Wise.«38» ".
So what is the measure in which the hand should be amputated? Hadith answers this question.
2. Should all thieves be punished in this manner? Hadith answers.( These are some of requirements for aplying this punishment: 1.The theft should not have taken place during famines and droughts, when the people are suffering from hunger and possess no means, 2. The item that is stolen should possess a value of at least one-fourth of a dinar, 3. It should have been stolen from a secured place such as a house, a shop, internal pockets etc. and other requirements)
3. How is Ghusl? what part(s) of the body should be washed in Ghusl (4:43)? Hadith answers.
4. How is Tayammom?
4:43 "And if you are ill or on a journey or one of you comes from the place of relieving himself or you have contacted women and find no water, then seek clean earth and wipe over( tayammamoo ) a part of your faces and your hands [with it]" What part of face or hand must be wiped over with clean soil for Tayammom? Hadith answers.
and so on... .
This answers are teachings of Qur'an. Qur'an is a set of principles and true Hadiths are interpretation and teachings of these principles.
Actually relating 12 Imams to this verse is just an imagination of Shia Muslims aas no one can stop Sunni to imagine this Ulil Amr being 4 Caliphs . That is unnecessary to discuss here as it is not mentioned in the verse . So let us ponder in the verse as it is .
Simply the verse says :
Firstly, ALLAH + Messenger + Ulil Amr = Follow them
Then, ALLAH + Messenger = Follow them
Why this elimination ? Because of the dispute . Ulil Amar are actually not any special group or persons rather people from us as the verse says , 'Ulil Amar minkum
...' means 'Ulill Amar from you ...' and the ' Fa in tazabtum...' means ' If you dispute...' .
This is also simple and an honest reader of the Qur'an won't go wrong to understand these like the way described above .
Dear Union, please read this verse more precisely: 4:59
"O (you who have believed)*, (obey Allah) and (obey the Messenger** and Owners of authority from you<minkum>***). And if you* disagree over anything, refer it to Allah and the Messenger".
In this verse, there are three ones:
* Believers
** Messenger
*** The Owners of authority.(Ulul Amr)
This verse says that belivers must do all commands of Allah(Quran), Messenger( Sunnah ), and Ulul Amr(those who can know Quran and Sunnah precisly without any fault and mistake).
So If believers*(who were addressed in the first part of the verse by Allah) dispute in anything, they should reffer legislation to Qur'an and Sunnah(What Ulul Amr can know and understand it
without any mistake, because the verse says we must do their commands, just as we must do infalliable Messenger commands) = they(believers*) should do the commands of Ulul Amr when Messenger is not with them, and also Ulul Amr order acording to Qur'an and Sunnah.
"Minkum" in the verse doesn't prove that Ulul Amr are some peoples like us, who aren't like Quran and Messenger infallible. "Minkum" indicates that Ulul Amr are believers and not Kafir, Jewish or Christian.
Please see this verse for minkum:
2:151 " ( O, believers) Just as We have sent among you
a messenger from yourselves(minkum) reciting to you Our verses and purifying you and teaching you the Book and wisdom and teaching you that which you did not know. ".
Minkum in this verse is exactly like minkum in 4:59.
And about "If you dispute in anything, reffer it to Allah and Messenger".
' You' refers to the beliviers* who the first part of the verse addressed them and doesn't refer to Ulul Amr***.Indeed, This part of verse says that when believers dispute, they should resolve thier dispute with the laws of Quran(Allah) and sunnah(Messenger) and when Messenger or Ulul Amr order any command, they shold accept and obey it. The next verse confirm this interpretation:
4:60 " Have you not seen those who claim to have believed in what was revealed to you, [O Muhammad], and what was revealed before you?
They wish to refer legislation to Taghut(Who doesn't order according to Qur'an and Sunnah = who is not Messenger or Ulul Amr), while they were commanded to reject it; and Satan wishes to lead them far astray. ".
There was Wahi already and specifically related to what Prophet Aaron was prohibiting them to worship the calf [Ref 26.16 ] . Prophet Aaron was not telling them to follow him in everything rather in the case of not worshiping the calf and only to worship the one real GOD :
[20:90] And Aaron had told them, "O my people, this is a test for you. Your only Lord is the Most Gracious, so follow me, and obey my commands."
[20:91] They said, "We will continue to worship it, until Moses comes back."
You have mentioned that:
There was Wahi already.
Hence it isn't correct which you say: Wahi only = holy Book(e.g. Quran). Right?