On step 4. there is missing one command:
# nmcli con reload
Without it, the new dns address will not be included in the configuration and the lab grade will result in FAIL.
Incidentally, nmcli con up <connection_name> will also work.
Section 15.5 of RH124 does it this way. Prior to seeing this, I'd use nmcli con down then nmcli con up.
Upon checking on section 11.11, nmcli con reload isn't necessary (although it doesn't harm anything) - it simply needs to exist as part of the connection configuration. The new IP address isn't used at that point. The student is told to reboot the system in step 6, which will activate the change.