Zaid Alsalami, Shaykh Dr Zaid Alsalami is an Iraqi born scholar, raised in Australia. He obtained a BA from Al-Mustafa University, Qom, and an MA from the Islamic College in London. He also obtained a PhD from... Answer updated 1 year ago

Bismihi ta'ala

At first we must differentiate between the seven methods of recitation of the Quran, and the concept of the descending of the Quran in seven letters or styles (aḥruf). The first is called al-qirā'āt al-sab', and the second is called nuzūl al-Qurān 'ala sab' at ahruf.

In regards to the concept of the Quran coming down in seven letters, the Shi'a view of this is that it is a myth and cannot be accepted. 

As for what does the word ḥarf  here mean, Sunni scholars have mentioned up to forty views for this. 

As for the Quran being preserved, this is the strong opinion of Shia Ulama. 

Please read this information, from al-Bayan, by the late A.U. Seyid Khoei.

https://www.introducingislam.org/info/7harfs/7harfs3.php