Did Leonardo da Vinci paint two Mona Lisas? Where are they?

There is only one Mona Lisa, at the Louvre, fully credited to Leonardo. However, there are several Mona Lisa look-alikes from his studio, some of them quite saucy. The one most similar to the Louvre one is the Prado Mona Lisa, a copy made simultaneously in Leonardo's workshop while he painted the Mona Lisa, probably made by an apprentice(s):

While overall similar, there are differences in the shape of the face, the background and other details.

Evidently there was a market for erotic paintings. The American art historian David Brown, curator of Italian Renaissance paintings at the National Gallery of Art in Washington, has suggested that da Vinci painted a saucy parody of the Mona Lisa for his patron Giuliano de Medici, and that the Salai version is a copy.

How can the citizens of Russia accept the enormous difference between people? The richest 500 Russians own more than the poorest 99.8% of the entire Russian population combined. Why don't we see any protests?

Then there are the ‘meza nuda’ paintings from his workshop, often referred to as Monna Vannas.

Obviously, the original Mona Lisa also inspired some cheeky versions of her.

Source: Chantilly, Musée Condé, France.

How can a native English speaker say "it was nice talking to you" in French without using that exact phrase?

Source: St Petersburg. Hermitage, Russia.

La Joconde nue:

Source: Louvre, Paris, France.

Algorithm to analyze smartphone app data can predict MS symptoms - Multiple Sclerosis News Today

Another version of the above exists, attributed to Salaj:

Donna Nuda:

For the one below, art experts suggest that it contains touches indicating that Leonardo contributed to it.

What happens when you get sick in a country with universal healthcare? What's the process like?