Launch an older version of an application by default?
If you want to open specific file types with a certain default application, e.g., .docx or .pages:

1) right-click on any of those files, hold down the option key and click on "Show Inspector". 

2) Choose your default application, e.g., Office 2011 Word, from the "open with" menu



3) Click on the "change all" button just below the "open with" tab