In answer to your questions:
1. You would ultimately need to use an updated language file to ensure that all strings are correctly translated. There is documentation on how these files are created on our
languages page, including information about translator benefits.
2. It would require customization on your part if you were looking to add functionality of other themes. Our themes are not encrypted though, so you are free to make modifications if you wish.
3. All support is provided within our forums, with more details relating to support found
here. Note that we do not officially support third party plugins or customizations.
4. The theme includes all the features outlined on the
Vantage theme information page, and the demo site is the default theme with no plugins, so that's what you get.
5. Vantage has a built in .csv importing tool which you can use to import data as seen on the
Vantage admin demo. Thanks.