"A series of questions I like to ask them." Dang, they must love you :)
Anyway, I'm facebook, snapchat, whatsapp, instagram, etc. friends with a few girls, but that's with ATFs who offered it openly. I'm not really interested in intruding on their real lives and searching for them otherwise, and in fact specifically avoid asking "a series of questions" that would let me pry into their real lives. That said, the algorithms on Facebook, WhatsApp, etc., are very aggressive, and I find it very common that I'll put a strippers phone number in my contact list, and she'll start showing up in my "people you may know" suggestion list, across a wide range of social media apps. I use a fake name and do not use a picture of my face on any social media site, so if I'm showing up in their "people you may know" lists also, they have no idea it's me. Anyway, there have been a few times I haven't been able to resist the temptation to peek.