You want to know the procedure to upgrade/downgrade the version of the SGOS firmware or Operating System on the ProxySG.

Refer to the following link for Symantec's documentation with details and complete instructions on upgrading or downgrading the version of the SGOS on the ProxySG (SGOS Upgrade/Downgrade WebGuide):

• https://origin-symwisedownload.symantec.com//resources/webguides/proxysg/upgrade_downgrade_sgos/Content/Topics/main.htm