Tips & Tricks
If I only have a UnityPro.STU File how can I open it in a Newer Version of Unity Pro

The information and methods presented here have not been validated for targeting Older Versions of Unity Pro

General Information regarding Unity Pro .STU, .STA, .ZEF and .XEF files

Unity Pro .STU, .STA and .ZEF files are actually compressed (zip) files that can be decompressed using typical file archiving utilities.  Each of these file types has a different purpose so the content is therefore different.  However, a .STU and a .STA can have some common content, this depends on many variables (user actions) and Unity Pro Project Settings.

Unity Pro .XEF files are purely XML for use with Unity Pro.  There is also common content between .ZEF and .XEF files, but for this content to be equal is also dependent on user actions (Unity Pro does not have settings for automatic management of Export Files).

How to create a UnityPro.STA file from a UnityPro.STU file

Using a file archiving utility, unzip the source UnityPro.STU file.  The result will be something like this...

Note:  The UnityPro.STU File must have been BUILT at least once for the BinAppli Folder to exist.

Next, select the BinAppli Folder in the Extracted Archive Content and zip this folder.  Rename the zipped file to YourFileName.STA.  Then open this file in your Newer target version of Unity Pro.