In answer to your questions:
1. You can add whatever categories you like to ClassiPress and create custom forms for each category so that users complete relevant fields when filling our the ad listing form for that category. There's certainly no reason why you couldn't use ClassiPress for this, and it really depends on what other requirements you want for your project as to whether or not you'd want to make additional customizations to the theme to suit.
2. By default, the location search functionality for ClassiPress is found on the category sidebar view as shown on the
demo site. Adding this to the homepage or creating other location based links would require customization on your part.
3. Yes, ClassiPress uses the native WordPress user functionality, so you can have as many admins as you need, regardless of where they are based.
4. Through customization, yes you can modify the default color options if you wish.
5. You can choose whether or not you wish to moderate ads before they are published, but yes your customers can complete their own listings.
6. & 7. ClassiPress is designed as a classified ads theme, but that's not to say you can't use it for business listings, however functionality such as events is not built into it by default in the way it is with the
Vantage theme.
Our themes are not encrypted, so you are free to customize it to suit your needs. AppThemes does not offer customization services, however we do have a
certified partners page where you can find developers for hire who are experienced at working with our products. If you make contact directly with an outline of your requirements, they can provide a quote for the work. Thanks.