if you're really really really really that anxious, just ask the other person, but yes, a friend of a friend in a friend group can be considered a friend
If they bother to share their time with you, no matter how it may be, and they enjoy that time they gave you, then they are your friends. Be it IRL or online.
Don't worry about it too much. In the end they're just labels.
What matters is the expectations you have of each other. Who do you enjoy hanging out with? Who can you be open with? Who can you count on when it really matters? They're all different types of friends, but they're all different lists you pick from depending on the situation.