Hello,
To be able to use Design Features/Elements between Niche Demos, you will need to Copy the CSS Styles from the Niche Demo where the element is used. Regarding the tabs, we have just released an Update: http://docs.semicolonweb.com/docs/changelog/version-6-0-3/ to fix the issue with Tab Content not displaying.
Meanwhile, as we have mentioned before, Customization Support is not provided and the Templates are provided as-is. Support is provided for the features and designs included with the Template. To add/modify designs or functionalities, you will need to manually code these or Hire a Freelancer to help you out.
Hope this Helps!
Let us know if we can help you with anything else or if you find any further issues.