Can Silverlight and ASP.NET MVC used together

Since Silverlight can fit into any HTML Container, MVC doesnt limit using Silverlight in MVC based webpages.

Is MVC useful for creating security applications

MVC is a pattern and Security is a practice.  While nothing can be generalized, Security of your application be it your MVC pattern or regular Webform pattern depends on the abstraction, authentication & authorization.

What are the extensions in case of MVC in .NET 3.5 and .NET 2.0

MVC doesnt have a specific extension.  Once you download MVC Bits, you get an MVC Application template in Visual Studio 2008.  The extenion for the webpage is normal webform (.aspx) and the controller & view are typically .cs or .vb files.

How can we use Form View control in MVC?

At the moment MVC Pattern doesnt fit in to using controls

Can MVC be used in multi-tier applications

MVC pattern adds an extra layer on top of existing layers such as Business Layer etc., and hence can be used with multi-tier applications

What is the main advantage of MVC over ASP.NET Form

MVC helps in creating test driven web development as well as separation of concerns into Model, View & Controller classes and hence helps in creating applications that can have friendly URLs