painting onto wet plaster
Fresco's weren't done in the middle ages. I think you are thinking of Renaissance artist Michelangelo.
giotto
The woman who painted over the fresco is Cecilia Gimnez, a Spanish amateur artist.
Do you mean wet or dry fresco? In both cases, you need alkali-resistent pigments. In wet fresco (the original fresco technique) they're mixed with the plaster used to finish the wall, in dry fresco (fresco secco) a paint is made with mainly caseine. I've seen an old recipe that involves fresh cheese (which contains caseine)
Diego Rivera
Two possible reasons: Oil paint on a smooth surface makes for easier painting small details than fresco paint on a wall. A fresco is usually a large-format mural, intended to be seen from a distance.
Fresco is created when earth tones are applied directly to wet plaster. The creation of paintings such as those within the Sistine Chapel were created in just such a manner.
The School of Athens is a famous fresco in the Vatican. It was painted in the early 16th century by Raffaello Sanzio, better known as "Raphael".
to make it easy
fresco
Leonardo da Vinci is the artist and scientist who painted the 'Last Supper'. The fresco is in the convent of Santa Maria delle Grazie in Milan. Considered to be in the movement of the Renaissance.
Mickey Fresco's birth name is Michael Fresco.