How do I activate my IPhone 5s?

How do I activate my IPhone 5s? - 1

Added (1). I purchased an AT&T iPhone 5s 16gb off ebay. The phone came in and it didn't come with a sim card. However everytime I try activating the phone just so I can use the apps and imessage and etc… It says please insert a sim card… Do I have to purchase one from AT&T or is there a way around this. Cause I really just want to get on the phone.

IPhone 6S Plus froze on the home screen, I was able to screenshot, and then I manually shut it down but deleted a lot of photos when came on?

I have iOS 11, the home screen froze, I could only screenshot, so I did that, then I pressed the side buttons to shut the restart the phone, but when I turned it back on, 1,000 of my 25,000 photos on my Camera Roll were gone

How to resolve this?

**Also, I haven't backed up my phone in 27 weeks, since most of the 1,000 lost photos were from 2015, would the photos still be in the latest backup from 27 weeks ago (before this BS happened)?

How can I stop this?

My iPhone will randomly start to play my ringtone but it remains on what I was viewing with no choice of being able to answer the phone so my ringtone is playing for no reason but can still be stopped by the lock button. Once lock button is pressed there's no missed calls visible. What's going on?