In v1.0 API I was able to get friends with their facebook ID like this:
{
\"name\": \"Somename SomeSurname\",
\"id\": \"100007797060798\"
}
/me/taggable_friends
shows all friends in the list except for some. In one case, there are 326 friends in a profile but this only shows 317 and in another profile there are 194 friends in total but it only shows 182.
$flist = $fb->api('/me/taggable_friends?fields=name,id&limit=1000');
shows almost all friends in the list (despite the limit being too high) but leaves some of them in both cases. This might not work on the api explorer if your app is not approved and published but it will work for admins, testers and developers of your application.
You cannot decode this id because that would defeat the purpose of encoding it in the first place.
What I am also wondering is that whether it is possible to invite friends of a user to use the application?