Silly Stop beating yourself up about it.
You did nothing wrong. Unadvisable yes and potentially dangerous but you were not a bad person for what you did.
I am 25 years old so 7 years younger than you. From 10 I had access to a computer and I did some unadvisable things from about 13 years old that I wont get into on here but feel free to private message me if you like?
To give a hint it involved similar things to you but naturally, at a younger age.
I don't like to blame but I felt very objectified and I liked the attention, if I'm honest - even now with a daughter and a fiancé due to certain things with an ex boyfriend and a girl from school my views on sex and relationships are still pretty fucked up, though I hide it well.
This man took advantage of a girl.
OK the talking/flirting bit may not have been illegal but asking you to strip/play with yourself was.
At age 14 I also spoke to an older block on the phone who was my then boyfriend's friend's best mate who stole it off his phone. He asked me to do these kind of things over the phone and made similar threats re: knowing where I was and some of the things he said was god awful! I was a little girl then actually really, in retrospect and he was 21 years old and having gone past 21 I know you have full control and understanding at that age.
Even if you were 21 him pressuring you, being emotionally manipulative, blackmailing and making threats was not OK. I know you know it wasn't OK, but I want you to really understand that all of that was his doing.
The only mistake you made was trusting someone you didn't know and most of us who grew up in the internet age (20-30ish now) have made that mistake at least once, albeit maybe not to the same extreme.
Keep him blocked. If he messages and friends tell them this: *He admitted to being a sick bastard who blackmailed and coaxed a young girl into doing illegal things for him? I'm glad to hear he's being so honest about his filthy behaviour."
If they think badly of you because of it, they are idiots.
I don't blame your parents as such either as they didn't know what this could potentially be like, similar to my parents. Now my parents know more about the internet they would not dream of letting my DD use it on her own without filters/it being in the same room as them. However, they probably should have read up more about it - the best thing to do if you don't know much about a topic.
Please feel free to private message me - please don't think badly of yourself, it's not your fault.
You were not dirty.
You were not weak.
You were not stupid.
You were not insert slang word that's meant to demonise a woman for showing any sign of sexual feeling at all
You were not to blame.
Sorry for waffling on - having been through similar I know how this kind of thing can eat you up but you have no reason for self hate or fear of this man sick bastard.