Did the Companions—may Allah be pleased with them—recite the entire Qur’an by heart in seven days to solidify their memorization, or from the Mushaf because it is superior, and does this apply to someone who has memorized the Qur’an?

There is no explicit text stating whether the recitation of the Qur'an was from the Mushaf (definition) (physical copy) or from memory. The matter is broad, and it is recommended for a Muslim to complete two recitations (khatmas) weekly: one from the Mushaf and the other from memory. It is preferred for the recitation from memory to be during prayer, especially at night, because reciting the Qur'an during prayer is superior to reciting it outside of prayer, and it helps in solidifying and perfecting memorization.