Your gallery is Photopost Pro
1. vbgallery is a separate product from photopost pro
2. answered above
3. The gallery will load whatever style the user selects. If you have custom styles you may need to edit each styles options and make any relative image directory paths full urls
4. That would depend on your servers image processors installed and what graphics libraries the server supports so this is not something we can answer without more info. Usually formats are jpg png tiff gif etc but your mileage varies.
5. my head always spins