If you own a network license, you can run the current version & 3 versions back. If you need an older version of your Autodesk product, you will need to request a Previous Use License. The instructions are noted here:
When you append the older code to the to the current license file and you parse the license file, it will look like this:
There is no need to request the entire license file on the SAME date because AutoCAD 2009 is looking for the Feature Code: 57600ACD_2009_0F.
Because we would like you to stay current, the older licenses are typically generated for the duration of 1 year from date of request.