Absolutely not. SDL Content Assistant is developed in-house and is powered by SDL Linguistic AI technology. You can trust that your content is not being sent to an external 3rd party service on the web.
This is not available on the user interface at the moment but you can request for this by contacting SDL.
Yes. If you wish to delete a project, open the project menu on the Project home page and click Delete. Once you delete a project, it cannot be recovered.