First consideration: strange choice of works, if one wants to talk about magic. I would be curious to know if it is a university exam, who the professor is and the university.
Let's get into specifics, even if briefly.
There is no magic in "La Cenerentola" and no magic in "Turandot"... the role of the fairy in Rossini's Cenerentola is, as is well known, taken from Alidoro, who is a philosopher or, rather, the master-counselor to Don Ramiro. Although it is an opera buffa, La Cenerentola is very close to semi-seria opera, of which the most blatant example is La Gazza Ladra, which will also be performed in 1817 but in May (Cenerentola in January). Despite being an opera with a very happy ending (goodness triumphs...), inside there are some "bourgeois" considerations and magic cannot be admitted (besides, I do not know of any Rossini operas in which there is magic...). Before the great Romantic era, magic is present mainly in serious operas, as a topos for sorcerous arias or for scenographic machines. Despite this, there is a small moment in the opera where something "unjustified" happens... in the second act, as usual, there is a storm, and because of this storm Don Ramiro's carriage stops right in front of Don Magnifico's house. Who caused this storm? I would say more fate than the hypothetical magic of Alidoro...
"Turandot" and magic... nowhere to be found. Nothing explicit, at least. There is the scene where Calaf hears the voices of the severed heads, but it could very well all be in his head. We might think that Princess Turandot's charm is otherworldly, perhaps a consequence of a sort of curse cast upon foreign princes, but these are all useless conjectures. From what I know, even the original novella by Carlo Gozzi from which the plot is taken does not speak of magic... therefore, an entirely incomprehensible choice.
"Lohengrin" is the only one of these works in which there is endless magic. More or less we can divide "Christian" magic from "pagan" magic; after all, Lohengrin is taken from the medieval German novel "Parzival" by Wolfram von Eschenbach... Lohengrin does not administer magic but is under the influence of a greater enchantment, that of Monsalvat, the homeland of the Grail knights, which does not allow him to reveal his own identity. Ortrud, on the other hand, is a true witch, who even transformed Elsa's brother into a swan. Any webpage will reveal to you the various Leitmotive dedicated to magic in this work; anyway, Wagner's entire creative trajectory is full of magical themes.