What is the reason for reading the Quran by substituting the letter Qaf with a letter resembling the Egyptian Gīm, and does this have support and origin in the successive recitations (Qira'at Mutawatirah), or is it not within the scope of the science of Qira'at?

Reading with the letter Qaf replaced by another letter is impermissible because it constitutes a change in the letter, its articulation point (makhraj), and its characteristics (sifah). None of the ten reciters (Qurra' al-Ashara) recited in this manner. Whoever intentionally alters a letter of the Qur'an disbelieves, as stated by Qadi Iyad: "Whoever intentionally alters a letter from the Qur'an disbelieves."