Hi,
If you are planning to add this unit back to the stack, i would recommend that you upgrade this switch to the same version of EXOS in the stack and boot the switch from the partition that is used by the rest of the stack units.
If you are thinking of using this switch as a stand alone unit, the below link gives you the information of the recommended version of EXOS for the corresponding hardware.
http://www.extremenetworks.com/extreme-hardwaresoftware-compatibility-recommendation-matrices/softwa...
Note: When performing the upgrade from the bootRom prompt, please try to use the GA version of EXOS and then upgrade the switch to the patch version that is used by the other units of stack if considering of adding this unit back to the stack.
Thank You,