The plans and prices on that website vary depending on the specific services and features you need. You'll have to visit the site to get the detailed breakdown.
It's hard to say exactly without further context. It could be a link to a specific post or page on Facebook, but more details are needed to determine its exact meaning.
It depends. Some people find it very useful and enjoyable for discovering new comics and interacting with fellow fans. But for others, it might not be that great.