I just tried downgrading the firmware on an RB433 from v3.25 to v3.23 (customer request). I believe that v3.25 is the original firmware.
After reboot Winbox showed a message saying I didn't have a valid license.
Software ID changed after the downgrade. Both ID's are of the form xxxx-xxxx
The page "http://wiki.mikrotik.com/wiki/Manual:All_about_licenses" confuses me.
I don't know if there was an old key in the files store or not.
Is it possible to downgrade from v3.25 to v3.23? Should I downgrade to v3.24 first?
Good news is that upgrading back to v3.25 "restored" my key.