This has been asked quite a few times and I don't think it's possible to display friend's information. Assuming you've done the basic work to display scores and leaderboards, I don't think there's anything beyond what's in the manual, nothing else was implemented in C2.
After doing some digging, community is having trouble getting a response here :
facebook-highscore-list_t64758?&hilit=facebook+friends&start=30
I don't think it's possible at the moment unless you do some javascript programming of your own, as mentioned in these tutorials where the user has modified the Facebook plugin:
https://www.scirra.com/tutorials/446/fa ... e-a-friend
https://www.scirra.com/tutorials/445/fa ... nds/page-5
You could integrate these into an android game if 1. and 2. were satisfied but I don't think it's possible, I could be wrong though.