I did #*LOGS# on my GSM Pre (with webOS 2.1.0) and I set mojo apps to log only errors and I set system logs to none, but I still have added new logs in /var/log/messages so what I must do to turn off EVERY SINGLE log on my Pre?
You can't. While you can turn off webOS-specific logging for the most part, the messaging through the underlying Linux install can't be turned off.
Turning off error logging won't provide any benefit unlike disabling "info" and "warning" logging.
If I helped you or you have downloaded one of my files,
then least you could do is click the "Thanks" button.