Nope. But I think it's a part of ClickOnce, the technology they use to bundle up an app into a setup.exe that fetches the latest source from a web server.
Nope. At work we have a similar setup.exe file. The setup.exe is a bootstrapper that installs prerequisites first, then runs the ClickOnce installer which is separate.
No such convention. Windows does some funky detection of when the exe might need to elevate privs but it detects anything with the word setup in the filename.