In answer to your questions:
1) By default, the author name will appear on the ad listings, so it would require some modification on your part if you wanted to hide this form the listing page, however it could technically be done. There is no encryption which would prevent you from making such changes to the theme.
2) This is not a feature available in ClassiPress by default, however you may like to check out the
Advanced custom fields plugin for ClassiPress which is available in the
AppThemes marketplace as this may give you the functionality you are looking for.
3) There is unfortunately no such feature in ClassiPress which would do this. You could achieve what you describe with some customization though.
Thanks :)