Thanks for writing in!
Please note that Expanded demo content is only for X Theme. Expended contents provide fully working website. Expended demo contents can be imported from X > Validation > Demo content. You can get more information on demo contents here:
Regarding addons, we ship premium plugins bundled with X Theme and Pro Theme which can be installed fro X/Pro > Validation > Extensions after validating X or Pro Theme.
Design cloud: Like I said, extended demo is only for X Theme. On the other hand Pro Theme comes with Design cloud that are premade design elements that can be imported using Design cloud. For more information, please take a look at following resource:
Absolutely. We are constantly working hard to launch demo demo contents. In future we do have plans to launch new Expended demo contents.