We have an
AppThemes customer showcase but unforutunatley we do not have any customer submitted Quality control sites at this time. You can see the theme overview and demo sites on the theme information page
here.
When you are assigned a ticket you can leave comments to indicate progress (basically document the process), include relevant notes and attachments, and once completed mark as closed. The milestones can indicate whatever it is that relates to your project, for example, software versions... what version you expect the issue to be resolved in. Yes, you can add your own values for these applicable to your project.
Quality Control and Vantage are separate theme, so they each require their own instance of WordPress to run. If you want both themes on the same website you would need to install them in a subdirectory:
e.g.
yourdomain.com <==Your Vantage installation
yourdomain.com/issues <== Your Quality Control installation
Thanks.