Which version of MVC am I using?

Open web.config file and find the System.Web.Mvc assembly definition:

assembly="System.Web.Mvc, Version=3.0.0.0 ..."

It's an MVC3 as you see. Via web you can use MvcDiagnostics which is similar to phpinfo() functionality in PHP.

Select the System.Web.Mvc assembly in the "References" folder in the solution explorer. Bring up the properties window (F4) and check the Version