What is the difference between AppleScript version and AppleScript Studio version?
Your first line of code simply returns the version of the AppleScript language currently in use. You can also see it under Script Editor → Preferences → General → Default Language.

As for AppleScript Studio, this is what Wikipedia has to say about it:


  AppleScript Studio
  A framework for attaching Cocoa interfaces to
  AppleScript applications, part of the Xcode package in Mac OS X 10.4
  and 10.5, now deprecated in favor of AppleScriptObjC.


— From AppleScript: the definitive guide, 2nd edition

In essence, it was what you used for creating AppleScript applications in Xcode.