In answer to your questions:
1. By default, users are required to register before they can post an ad, however
plugins such as this can allow anonymous posting. Featured ads and use of the featured ads slider is optional based on ClassiPress settings. You can create custom ad listing forms if you're looking only at a specific set of fields, you can also determine the number of images from the admin dashboard.
2. The advanced search is visible in the category view sidebar, and there you can specify location based search fields as shown on the
ClassiPress demo site. Outside of this, it would require customization on your part if you wanted to allow country selection first from the index page.
3. You can disable registration which means that others would be unable to register and post ads.
4. We sell only the themes, and pricing can be found
here. You would need to organize hosting and domain name services yourself so the cost depends on who you sign up with. You can find information about our WordPress Hosting promotion
here which could save you money on your theme purchase. Thanks.