In answer to your questions:
1) Yes, Vantage includes the PayPal payment gateway by default (as well as a manual/bank transfer option), however you can also purchase
additional payment gateway plugins from the
AppThemes marketplace if you wish.
2) This depends on what kind of payments are supported for your specific country by
PayPal.
3) This is outside the scope of what the theme itself manages, but you could check the PayPal site for more information if required.
4) No other plugins are required in order to use the theme, but there are those optional ones available in the AppThemes marketplace as linked above, and
other plugins you can look at if you wish.
5) A listing is specific to a company, so I'm not entirely sure what you mean? Please feel free to clarify further and I'll be happy to address this question properly once I have a better understanding of it.
Thanks.