Since there are some unfrequent changes to the gpgnet protocol, old versions would not work with the current FAF lobby server.
Thus you will not find official support for running old versions.
In theory, if you start an older replay, all the files of that replays patch level get installed. But you cannot play online via FAF, but would have to play via LAN or some other solutions. I don't know to which extent this is currently possible.
