I have not used Craft much, but can I setup multiple sites under one Craft install?
If I can, which version of Craft is needed?
you definitely can, both in Craft 2 and Craft 3. I would recommend using Craft 3 (3.1 beta if you can) so you use the latest improvements available.
On Craft 3 you can set different Groups for different pages and then different sites within each group for the different languages.
I recommend this video, it helps a lot with the set-up and understanding how it works.
Anyway, I am not sure if you might need different license type for setting more than one site on production.