1. You can config to lock the content of a article by a “Social Locker Module”. To do that, instead of adding content to article, you add content that you want to lock to a “Social Locker Module”, then load that Social Locker module to the article.
For more information, you can refer the section “#2: Load module into articles” : http://www.joomlart.com/documentation/joomla-module/ja-social-locker-documentation#display-module
2. CSS is used only to style the page. As I said above, currently, this module supports only three 3 social networks: Facebook, Google+ and Twitter