How do you get cydia?

I want to get cydia on my iPhone, I'm currently running iOS 11.2. Can someone tell me where to start

Make any earphones bluetooth with a dongle-like device?

I remember a few years ago when I first got an ipod, I had a little dongle-thing, that plugged into the ipod and made it transmit my music via FM radio, so that it could be picked up by a car that didn't support aux input or usb input at the time.

I recently got the iPhone 8 which only has lightning input, and I was wondering if there was a device that you could plug earphones into, that received music from your phone via bluetooth, and plays it through the earphones? I have a pretty expensive pair of Bose earphones from a few years ago, and the sound quality is still really good, and I begrudge buying bluetooth earphones because of this.

Have I broken my IPhone 6 plus?

My phone fell from the top of my chest of drawers on to the (carpet tiled) floor, while in it's silicone case,

There was no screen damage and it seems to turn on and work fine?

This is my first iPhone, so I don't whether it's okay too leave it or whether I should take it in to be looked at?

Is it a ghost or some malfunction?

So my iPhone 7 keeps switching on to Siri like around 1 am and it usually starts with Siri popping up and the chat says hey Siri even tho I never said anything and I don't know if it's a ghost or a common problem?