Be sure the demo site is updated when ever a release is made, to prevent demo administrators from seeing a warning when entering the Administration Control Panel and elsewhere during the time gap.

Else they see
"Your phpBB installation is not up to date.
Re-Check version · More information »
Warning

Please delete, move or rename the install directory before you use your board. If this directory is still present, only the Administration Control Panel (ACP) will be accessible."