What is the response to those who impugn the Noble Quran, relying on the discovery of manuscripts in Yemen that contain a lower layer with verses different from the Uthmanic Mushaf, claiming the original Quran has been distorted?

The fundamental authority for judging the authenticity of printed and manuscript Qur'ans is the preserved Qur'an, transmitted by continuous, successive narration (tawatur) across generations, not by comparing it to other copies. The Qur'an is preserved through this unbroken chain of narration, in which reciters only differ within the bounds of the known recitations (qira'at). As for the Sana'a manuscripts, which date back to the early centuries of Hijra, no distortion deviating from the 'Uthmani script of the Qur'an has been found within them. The claim made by the Orientalist Gerd Puin regarding the existence of differences in some "palimpsests" (ṭurūs) is mostly due to students' educational errors and does not indicate any change or development in the Quranic text. This has been proven by specialized studies and refuted by messages from other Orientalists.