Having ssh-access, you can modify the file that is used for checking the current version. That would be the file /img/version
So if you type 'cat /img/version' you should see the currently installed version (e.g. 1.00.04.2).
As you want to downgrade to version 1.00.02, you should make the system think that the current version is 1.00.01. Then 'upgrading' to 1.00.02 is allowed. If you want the system to think that the current version is 1.00.01, you can achieve this by typing 'echo 1.00.01 >/img/version'
Now you can 'upgrade' from version 1.00.01 to version 1.00.02 (and in fact downgrade from 1.00.04.2 to 1.00.02)