I have one ePO server running on the old and unsupported 3.6.1 version. The other day from the ePO console I re-installed the VSE 8.5 software from the deployment task and later found out this caused the server to reboot. I've uninstalled/installed McAfee from ePO before and this hasn't happened. Is it possible for ePO to force a reboot?
Yes, ePO has always been able to do this - it depends on how the agent policy is configured. (It doesn't force reboots by default, as far as I know, but it's user-configurable.)