Which is the correct pronunciation of the letter "Rāʾ": "Rāʾ" or "Rā"? And should it be pronounced "Rā" when it appears in the opening letters of chapters, such as "Alif, Lām, Rā" in Sūrat Ar-Raʿd?

The correct way for the letter "Rāʾ" is to prolong it (madd), but it is permissible to shorten it (qaṣr) out of poetic necessity. This has been indicated by the writings of linguists and reciters, and by their pronunciation. As for not prolonging it in the opening letters of the surahs (fawātiḥ as-suwar), this is because the Quran is an argument against others, and the matter revolves around the authenticity of the narration. The ten reciters have transmitted by continuous, unbroken chains (tawātur) the non-prolongation of letters ending with a hamza in the opening letters of the surahs (such as Rāʾ, Ṭāʾ, Yāʾ, Ḥāʾ, and Hāʾ), in contrast to what they prolonged in Qāf and Ṣād.