1.You can use Visual Studio not only for creating Master Pages and User Controls but also for classes, implementing some specific logic that will be used in the User Controls for example.
2.Yes, Sitefinity is shipped with the whole RadControls suite. Some of these controls are used in the Administration section; also, you can use each of the Rad Controls in your User Controls or you can add them to the Sitefinity Toolbox through web.config.
3.Currently, Sitefinity doesn't support Public users, but you could always add such functionality. We intend to provide Public users module in the next version of Sitefinity. For the time being we can recommend the following two approaches:
• use the same Membership providers as CMS users implementation. You should define a specific role for the Public users to separate them from CMS users.
• use different Membership providers. In this case you will need to crate a second login form for the Public users and specify provider name. Note that different providers can use the same or different databases.
If you come up with more questions, do not hesitate to contact us.
the Telerik team