Does the reward of a Quranic حافظ (memorizer) who is certified in the ten Qira'at (readings) multiply, and does he ascend to higher ranks with every verse he recites using them? And does he have a multiplied virtue over one who has memorized with only one Qira'ah?

The reward for reciting the Qur'an is obtained by every reciter who recites correctly. The reward is tied to the quantity of recitation, not its variety, as the Prophet, peace and blessings be upon him, said: "Whoever recites a letter from the Book of Allah, he will have a good deed for it, and a good deed is ten times its like. I do not say that 'Alif-Lam-Mim' is a letter, but 'Alif' is a letter, 'Lam' is a letter, and 'Mim' is a letter." Thus, the reward is tied to the simple letter. There is no difference between reciting a verse or a surah twice with one narration or once with two narrations. However, one who is skilled in recitations may have an additional reward due to their increased knowledge and effort.