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.
You can create more than one template to provide layout and style alternatives with the use of the template selector.
Yes, the component link field supports both internal and external URLs.
Yes, this is possible by creating a custom element.