If I change a Helper layout, will it change where it's used?
No. Helpers are coupled with the page once placed. Changes to the Helper layout will not affect existing instances.
Acquia Cohesion renames to Site Studio from version 6.2. Tell me more.
The 'Range' in the menu list item element sets which list items at the current level the settings should apply to.
Yes, the component link field supports both internal and external URLs.
No, the entity browser does not work for component defaults as the entities are content, not config.
Yes, this is possible by creating a custom element.