Is it true that Ayatul Kursi has servants (khuddam), and that reciting it a certain number of times during the day and night protects a person from devils, cures them of illnesses, and aids them in acts of obedience, and is the one who does so sinful?

The belief held by some regarding the existence of a servant (khadim) for a verse or surah from the Quran is a false belief. It has been established that Ayat al-Kursi protects a person from jinn and devils during sleep, as narrated in the hadith of Abu Hurairah that Satan informed him that whoever recites Ayat al-Kursi before sleeping, no devil will approach him until morning, and the Prophet, peace and blessings be upon him, affirmed this.