[dnanian]

Hi, Emily, and welcome.

It's absolutely fine to be booted from Sandbox and then back up your Macintosh HD to the backup location. In fact, it's the right thing to do, and there's no reason to be actively booted from a drive to back it up.

In general, you don't have to log out and back in with Shift down. We suggest it, though, mostly because it avoids problems that can occur. If you're not running into any issues, you can go right ahead and not log out.

Repairing permissions happens on the drive you select, so if you select Sandbox it works on Sandbox. I'm not sure what you mean by "run scripts, etc", so I can't answer.

We have some tips about Tiger on a Sandbox in the FAQ under Tiger Compatibility. It's important to note that Tiger changed the way it stores mail and iCal data, so recognize that steps need to be taken if you want to "roll back" to Panther.

Hope that helps!