What is the ruling on one who speaks about the Qur'anic readings without knowledge and recites a Qur'anic word in a way whose authenticity he does not know, and how does he repent from this act?

It is a grave error to intentionally speak about the Quran without knowledge. Whoever does so must repent, based on the hadith (definition): "Whoever speaks about the Quran without knowledge, let him take his seat in Hellfire." And the hadith: "Whoever speaks about the Quran with his opinion and is correct, has erred." Its meaning is: Whoever speaks about the Quran without a legitimate religious or rational proof that conforms to the Sharia (definition), or without following the sayings of the Imams, but rather according to what his intellect dictates, has erred from the path of rectitude, even if he happens to be correct.