Advice request: automating SD!

[SteveL]

I'm setting up a college student's iMac and need some expert advice.

1. Schedule Backups. The manual states, "SuperDuper! does not have to be running for a schedule backup to take place, but ... the screen must be unlocked." What does "unlocked" mean? The iMac will be configured to wake up one minute before the SD! backup, but it is password protected. If it's password protected, does this mean that the screen is "locked," so SD! will not run?
   
2. Disk. Is there any reason that I shouldn't partition an external USB drive and use one partition for a SD! clone and another partition for TimeMachine?
   
3. Open Applications. When I run SD! I meticulously make sure that all programs are closed, etc. What happens if SD! runs and several programs are open, such as Safari and iTunes for example?

Thanks for your advice and tips!!