The last time when I had done web development in asp .net was 6 years ago and there are so many type of tools available now. Hope to get some advice on the approach to build a social networking website.

Should i start building the site using tools such as umbraco and continue to work on it using asp .net on areas that umbraco cannot satisfy? (not sure whether a site generated by free version of umbraco allows modification using asp .net in VS or visual web developer).
Or could either umbraco or asp .net alone serves the purpose? The site built should be extensible and scalable to cater for more features and more users in the future.

The features include:
1. facebook-like basic features such as invite friends, add friends, allow granting friends or all to view personal profile.
2. Paragraphs of a topic is displayed on the left side of the page and comments specific to a paragraph could be added next to it on the right side. Comments could be provided by multiple users thus a neat for the presentation is essential.
3. While an user is viewing a topic, any new comments added by other users should appear simultaneously like the live feed and news feed features in facebook. (if this requires huge effort then i may have to put it under future enhancement and consider alternatives for now)
4. Add-on new paragraphs to a topic, a feature like wiki's.
5. search topics and friends (wild-card search instead of exact match search)

Let me know if any clarifications are needed. Thank you so much!