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, you can build mega menus using Cohesion. Building mega menus requires advanced knowledge of jQuery in Acquia Cohesion and CSS.
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.