Social Network/ twit application/ min blog

I want a system that allows users to follow other system users just like on the twitter site, they will be able to comment on topics/ issues published by the users and vice-versa. Users will have a profile that they will manage just like the face-book website, but with minimum applications. The application needed will include a user information that are not personal/private, pictures, and friends list, including the Topic/ Issue that they want their followers to discuss on, and also displaying each users statement to the topic that has been uploaded by the profile owner Every user will be able to comment on every uploaded Topic/ Issue made by other system users, but the system should be able to differentiate on the users profile between the comments made on the Topic/ Issue, by a public user which are users that are not friends with the profile owner and those users that are not public in this case, users that are friends with the profile owner. The system will also have its own topic (One Major Topic) that will be uploaded by the system administration, and it should be the main focal point of the system as the aim of the system is to get all users to discuss this main Topic/ Issue. With this focal main Topic/Issue each user should have a link to it on their profile, and on it they will be able to see the comments made by all the users of the system on one tab and the filtered comment made the users that are their friends on the next tab. The public tab should include the comments made by the general users including their friends. The focal system should also have reservations for video uploads. The system will also include an application that enables users to suggest what should be made the Main Topic/Issue. All comments should have a 80 -150 word restriction, this include the uploads, the comments and every other thing that the user will be able to comment on.