1) Yes, you can change the field values from within the ClassiPress admin
2) I believe there are image size plugins such as
this, but it's not one of the specifically recommended plugins, so not officially supported.
3) You can see for yourself if you check out the
ClassiPress demo. There are some differences such as rounded corners don't show in IE, however this doesn't effect functionality.
4) The currently available promos are related to
AppThemes translators and
WordPress Hosting.