What's the best way to integrate Facebook into my Unity game?

(This question is about Facebook's Unity SDK and Facebook integration into Unity.)

Hi all.


I would really like to have some of my questions about Unity and Facebook integration answered, but wherever I search on the web they are not even mentioned. Could anyone be so nice as to provide answers, or at least a point-in-the-right-direction?


--> First off, do games played on Facebook Canvas have to be free? That is, is there any way to charge an upfront cost to install or play a game on Facebook Canvas, like a "premium" game found on the App Store or Google Play?


I'm asking this here because it's not mentioned on Facebook's side, and there might be some people here who have experience with the issue.


I ask because I'm toying with the idea of monetizing the current game I'm working on, and I don't approve of using In-App-Purchases (for reasons that will not be discussed here), and they wouldn't even make sense to use in this game.


However, my game would naturally be more fun, fulfilling, and marketable if players could share their scores on Facebook, whether through Requests or Open Graph Sharing (see the documentation in the Facebook Developers section of Facebook).


And the success of the game would probably depend on word-of-mouth and social chatter on Facebook if it was a premium game, I figure.


But the rest of the game functionality would not be web-based or Facebook-based, but would run on the local device (iOS and Android).


--> Is it possible to fix the mobile versions (iOS and Android) of my game so that after a player scores high enough to please him or her, he or she could tap an onscreen button to log into Facebook and then post the score on his or her timeline and newsfeed? Using Sharing with Open Graph?


Another thing that confuses me greatly, is that the Facebook Developers' section mentions that Sharing does NOT require Facebook Login.


--> How can someone send a Share if he or she is not logged on to Facebook? Or, otherwise, what do the Facebook docs mean by "Facebook Login?"


--> Is all of this possible with a game for mobile devices that doesn't connect to Facebook (or the internet) at all other than to Share information in the newsfeed?


Can anyone help me to understand this situation better? Is there anything else I need to know, or explain further?


Thanks!