Yes, when you are in a 5.00 module the "CAESAR II" archive is exploded, and you could copy the _A file someplace else. However, once you save the data in a newer version, most of the time you can't reopen the file in an earlier version. This is because of the new data added for the newer version.

As an example, Version 5.00 expanded the input to carry an additional 9 values of elastic modulus. Version 4.50 can not handle this - it is unexpected data, the Input Processor would simply crash attempting to read this file. Therefore, we check version numbers, and if unacceptable, we put up the error message and quit.