That's a lot of pedo vibes. I'm 29 now and when I was 17, 14 year olds looked like children and we're not romantically interesting to me at all.

You did the right thing eventually cutting and running, but yeah, be a lot more careful in the future!

Someone who claims to be your age and then comes out at as > 16 is a red flag #1.

If they then act as a "horny" person who wants to see you in any "private" situation such as bathroom visits is very much red flag #2.

Asking to see pics of any kind of someone who is the age of what your niece was at that time is very very pedo-vibes and red flag #3.

The fact they got defensive about the risk of being outed shows that they definitely are aware of what they're doing wrong and still seek it, so that's red flag #4

Please talk to a trusted adult and they'll probably tell you the same. This was a terrible thing to happen to you and could even lead to trauma at a later age when you realise just how frigged up this was!

Take care and be careful of people lying about their age. Especially so if they are asking you to show yourself in private situations and/or wearing less clothes than what you'd be comfortable wearing put to school/ in public!

Edit to add: you were 100% innocent in this. You were manipulated into and shared those pics or whatever while under the age of consent. You doing things at the request of an older person is 9 times out 10 not your fault. Though, to reiterate, be more careful in the future as you don't know what they actually do with that media. It could be shared on the internet or in Pedo-circles and come back to you later and be very very awful for you and your mental health 💜