PHP registration page and users profile update

I need my current registration page broken down into several screens which the users works through. I need to be able to alter the questions in the registration page via my admin section. I also need to assign in the admin section if a field is 'required' (i.e. if the user does not fill in, an error message will show.) This registration page has the details that will form the users profile. In my admin, i need to be able to select the parts that will show on a users profile e.g. username, location, about me etc.