Unleashed firmware Releases occur transparently to users, by development engineering on a Cloud server host, usually overnight.
Admins on the Master AP, can go to Administer -> Upgrade page, where current firmware version is shown (ie 18.104.22.168.55).
Admin needs to click the Software Upgrade button, in order to 1) check Cloud server for newer version 2) Initiate network firmware upgrade (when available).
There is no facility to Downgrade an Unleashed network. It is not recommended to install earlier Unleashed versions. Earlier Unleashed version APs that join the network, will be updated to the current release running on the Master AP.