Unknown device on my iCloud account?

I'm actually so confused right now. This random iPhone 8 plus popped up on my iCloud account. I've asked everyone I know if its theirs so now i just wanna know how to remove it so they can't see my pictures, messages, and stuff.

Forgot my passcode on my old phone?

I want to give my dad my old iPhone 5SE, but I forgot the passcode. My friend told me that unless iCloud is on, apple can't retrieve the passcode, is that true?

What is wrong with my phone?

So I have an iphone SE and my friend stole it from me and dropped it. There are spots that are brighter than the others and a mark in the middle of my phone, it's on the screen so it's not my camera. Is my phone gonna stop working? Because the same thing happened to my other phone and it stopped workin. Is there also any solutions? Thank hope my explanation made sense. 😂

Was this person overeating?

My friend and I are in college. The seniors in our class were doing a "invention fair." They were all business students presenting our ideas and prototypes. As freshmen, our job was to take photos of the event for our college's Facebook. We know all the seniors and were on friendly terms. My friend was taking photos but was not asking permission since she was friends with everyone. Then one guy slapped her phone on the floor and the screen cracked. She has an iPhone. I know its her fault for not asking permission, but I think he should have told her to stop and delete the photos instead. She want him to pay for the screen. Does she have a case?

Added (1). Was this person overreacting? Sorry for the typo.