1) Admin demo can be viewed here: http://classibase.com/support/try-classibase-demo/
2) Can you clearify which SEO tags you mean? Script uses Title, description tags based on posted item and category name and descriptions. Also you can add any custom html to header or footer. Also script uses Schema for breadcrumbs and posted items for SEO.
3) No, script does not have support for sub-domains. City, country, categories, locales are all used as directory structure.