Where are updates downloaded to?

I'm trying to write a detailing the Shavlik Patch architecture and hava few questions.

1. Where does Shavlik Patch download the patches to before they are published into WSUS?
2. Does the patch download happen during catalogue synchronisation or when they are published to WSUS?
3. Do the patch files get transferred into the WSUS updates location when they are published?
4. What the options for rollback of a patch with Shavlik Patch?  Is it custom actions and scripts?

thanks