Often in Polemical arguments, the issue of the Quran’s variant recitations is raised to cast doubt and dispute
the preservation of the Quran. However, Muslims (who are sufficiently versed) are aware of these variant recitations and traditionally accept these various readings [particular methods of reciting the Quran] as authoritative (i.e. attributed to Prophet Muhammad
peace be upon him). Although, the laity may not be versed or even aware of these various methods of reciting the Quran, in general they accept that there are various authorative readings. Many well-versed reciters of Quran have learnt, recited and imparted
these readings for centuries and continue to do so.
It is alleged that the Qur’ān has variant
readings. Typically a verse may have more than one variation. These variations are not merely in pronunciation, they exist, for example, in addition or deletions of words, in the singular and plural form of words, in declensions and in verb structures. It
is generally believed that these variations have been divinely revealed.
Most scholars acknowledge that the ‘variant readings’ of the Quran need to be transmitted by the multitude (Arabic: Mutawatir) from the contemporaries of the Prophet (peace
be upon him), for validity.
There is no difference of opinion about the fact that whatever is contained in the Qur'an is Mutawatir [transmitted by multitude]
both in totality and in part. To the Ahlu'l-Sunnah, the placements therein and its arrangement are all Mutawatir so that it [the Qur'an] becomes indisputable. This is because it is an acknowledged fact that the Qur'an is a document whose details
desire Tawatur [transmission by the multitude]…. Consequently, whatever part of the Qur'an has been transmitted through the Ahad (isolate reports) and is not Mutawatir is unquestionably not the Qur'an by any means. (Suyuti, Itqan Fi 'Ulumi'l-Qur'an, 2nd ed., vol. 1, [Baydar: Manshurat al-Radi, 1343 AH], p. 266)
the chains of narrators of these variant readings are examined, none of them can be claimed as Mutawatir [transmitted by multitude]. They may be Mutawatir from their famous originators but they are certainly not Mutawatir all
the way from these originators up to the Prophet (peace be upon him). At best, they can be classified as Ahad (isolate reports). An example would suffice to illustrate this. Following are the three ways in which one of the Qurra', 'Asim Ibn
Abi Najwad Al-Bahdlah (d: 127 AH) has [supposedly] narrated his reading from the Prophet (peace be upon him):
Prophet Muhammad (peace be upon him), 'Abdu'llah Ibn Mas'ud, Zirr
Ibn Hubaysh Abu 'Abdu'l-Rahman Sullami Abu 'Amr Shaybani, 'Asim Ibn Abi Najwad, Hafs Ibn Sulayman Abu Bakr 'Ayyash.
Prophet Muhammad (peace be upon him),
Zayd Ibn Thabit Ubayyi Ibn Ka'ab, Abu 'Abdu'l-Rahman Sullami, 'Asim Ibn Abi Najwad, Hafs Ibn Sulayman Abu Bakr 'Ayyash
Prophet Muhammad (peace be upon
him), 'Ali 'Uthman, Zirr Ibn Hubaysh Abu 'Abdu'l-Rahman Sullami, 'Asim Ibn Abi Najwad, Hafs Ibn Sulayman Abu Bakr 'Ayyash.
The above example illustrates the fact that the ‘variant readings’ of the Quran are not Mutawatir (transmitted by multitude) from the Prophet (peace be upon him):
…However, one opinion is that they are Mashhur [renowned amongst the scholars]… The truth in this regard is that they are Mutawatir from these seven [Qurr'a]. As far as
their Tawatur (multitude transmission) from the Prophet (peace be upon him) is concerned, this is debatable. For the chain of narrators of these seven are found in the books of Qira'at. These chains are transmission from a single person to another
and do not fulfil the condition of Tawatur [multitude] neither from the first narrator to the last nor in between. (Zarkashi, Burhan, 2nd ed., vol. 1, [Beirut: Daru'l-Fikr, 1980] p. 319). 
To perplex the matter further - …not only are these readings isolate reports (Ahad), but also many of the narrators of these readings
are not regarded as trustworthy by the scholars of 'Ilmu'l-Rijal [biography of the narrators] as far as accepting Ahadith [tradition of the Prophet] from them is concerned. Thus, the inconsistency
of accepting such unreliable narrators concerning the ‘variant readings’ of the Quran is evident.
So why do the clerical
class of Muslim scholars accept the so-called variant readings of the Quran?
Perhaps they deemed that if they did not accept these reports, they would have to reject
or cast doubt in the vast reports regarding the Prophet’s alleged sayings, actions and tacit approval or criticism (i.e. Hadiths).
However, what is being read by the common masses and accepted or agreed upon - both by the common masses and scholars alike, is only one version of the Quran. That has been transmitted from
the common masses of the contemporaries of the Prophet (peace be upon him) to next generation of common masses and then to the next perpetually.
Many Muslims are 'programmed'
into accepting the deductions and opinions of the clerical class of Muslim scholars without any critical thinking or mechanism of verification and thus often have the impression that the status of the ‘variant readings’ is that of The Quran. While
at the same time denigrating the various versions of the Gospels or the Bible based upon the very similar premise, yet they are expected to accept the ‘variants readings’ of the Quran.
Albeit these variant readings are insignificant in regards to the overarching message found in their manuscripts and are in the main agreeable to the universal reading of the
Quran. Nevertheless, these ‘variant readings’ have no authorisation from the Quran’s perspective but have come about due to secondary sources.
Naturally, human errors may have occurred in some manuscripts or codices of individuals, but it is cogent to conclude that God preserved the universal reading
of The Quran not only in the written form but via the en masse oral transmission of the common masses from generation to generation which superseded any written manuscript transmitted by individuals.
Hence, indeed, We made this Qur’an easy to bear in mind: who, then, is willing to take it to heart? (54:17, 22, 32, 40)
Verily We: It is We Who have sent down the Dhikr (i.e. the Quran) and surely, We will guard it (from corruption). (15:9)
Nay! This is a Glorious Quran, (Inscribed) in Al-Lauh
Al-Mahfuz (The Preserved Tablet)! ( 85:21-22)
Which falsehood cannot touch from any angle, a Revelation sent down from the Wise One, Worthy of All Praise. (41:42)
Verily, Upon Us is its collection and recital. So when We have recited it follow this recital [of Ours]. (75:17-18)
It is clear from these verses that the Almighty recited the Qur'an in a single reading. The words leave no room for multiple readings of the same word or verses. Furthermore, the verse emphatically instructs the Prophet (peace
be upon him) to follow ONLY this particular recital. 
This recital is well known and practised by the common masses today, conveyed to us by the contemporaries and earliest followers (en masse) of Prophet Muhammad (peace be upon him) a task ordered by God
Almighty. [22:78], [6:19]. Naturally, it was written down and compiled from the outset (contrary to conventional belief). [80:13], [98:2] [75:17]. There is absolutely no warrant from the Quran to suggest that
there are variant readings of the Quran. All suggestions otherwise come from a later extraneous material 'faithfully' conveyed by Muslim sources despite the fact that the accounts are unreliable. Thus, all secondary sources must be subservient
to the Quran. [25:1]
And Allah knows best.
 As an example, this is what is written about Hafs Ibn Sulayman, perhaps the most famous and most widely acclaimed of all the disciples of the major Qurra
'Abdu'l-Rahman Ibn Abi Hatim, 'Umar Ibn Shu'ayb Sabuni, Ahmad Ibn Hambal,Bukhari, Muslim and Nasa'i call him Matruku'l-Hadith (From whom Ahadith are not accepted) .… In the opinion of Yahya Ibn Mu'in as
quoted by Abu QudamahSarakhsiand 'UthmanIbn Sa'idhe is not trustworthy …. 'Ali Ibn Madini says: he is weak in matters of Hadith and I have forsaken him voluntarily. …. Abu Zur'ah alsosays that he is weak in matters of Hadith ….. SalihMuhammad
Al-Baghdadi says the Ahadith narrated by him are not worth writing and all of them mention unfamiliar things in religion. Zakariyyah Ibn Yahya Al-Saji narrates from Sammak and 'Alqamah Ibn Marthad and Qays Ibn Muslim that his Ahadith are not reliable ….
'Abdu'l-Rahman Ibn Abi Hatim says that he asked his father about Hafs. His father said that his Ahadith are not even worth writing. He is weak in matters of Hadith, cannot be attested to and his Ahadith are not acceptable. Abdu'l-Rahman Ibn Yusuf says that
he is a great liar, worthy of being forsaken and forges Ahadith. Hakim Abu Ahmad says: He wastes Ahadith. Yahya Ibn Sa'id says that he took a book from him but never returned it. He would take books from people and copy them. Abu Ahmad Ibn 'Addi narrates from
Al-Saji and Ahmad Ibn Muhammad Al-Baghdadi and Yahya Ibn Mu'in that Hafs Ibn Sulayman and Abu Bakr Ibn 'Ayyash are the most competent of all who know the reading of 'Asim. Hafs is even more competent than Abu Bakr. However, Hafs is a great liar while Abu Bakr
is reliable. http://www.javedahmadghamidi.com/books/view/the_quraan_has_variant_readings
 This is alluded to, by the scholar Javed al-Ghamidi: http://www.javedahmadghamidi.com/renaissance/view/variant-readings