Yes, For the engine only (Excluding Blueprint) uses C++.
No, C# is not a Upgraded version of C++. It is a C ‘like’ language. Though here is the link to learn more.
For I Probably messed that up! C Sharp (programming language) - Wikipedia
Also, for the 3d graphics, Maya is the best. But! You can use blender for free instead of paying a ton of money!