Hi:

Here is an idea to have backwards compatible with different versions of SOLIDWORKS.

The workflow is like this:

1. In SOLIDWORKS 201X/Y/Z, use this Backward Compatible to Save the SOLIDWORKS file as a Macro file. (.swb)
2. Open this Macro file in different version of SOLIDWORKS 201A/B/C , edit the file, and use the same tool to save the changes back to the Macro file.
3. Now open this Macro file in SOLIDWORKS 201X/Y/Z  to see the changes.
4. Using this method, the model with full feature tree will be preserved in different version of SOLIDWORKS.
5. The features used in this kind of  version-free file are limited as API changed in different SOLIDWORKS versions.

1. Part downloaded from http://b2b.partcommunity.com/ are in swb format . (see attached)
2. Obviously, the company CADENAS PARTsolutions has some tool to use simple features (Extrude, Revolve, Cut-Extrude, Revolve-Cut) to model a part and convert it into SOLIDWORKS Macro file, the API for basic features like Extrude, Revolve, Cut-Extrude, Revolve-Cut did not change a lot over the time, and it can realize backward competitive for many versions.
3. Similar concept actually are applicable for other CAD software as well.
4. Another Benefit of using this method is the file size is much smaller, the Macro after zipped is 20,480 bytes, the part model file size is 1,114,112 bytes, this is 50x of compression rate!

Reference:

SolidWorks Macro - CADENAS PARTsolutionsCADENAS PARTsolutions