The frontend testimonial user submission has to be configured from:

• The global settings > Enable frontend testimonial submission/edition
• The permissions (extension configuration) > Do a fine tune on action per Joomla user group

More information can be found in the documentation.

Yes, if you want to. From the global configuration make sure that "Rich Snippet" is enabled (it is by default).

This is quite simple, open the extension configuration and feel your company information. The company information will be added into the search results and in Google Maps too (if you got a physical address).