Can I sell an iPhone before it's paid off?

I'm looking to upgrade my phone; I'm currently financing an iPhone 7 with AT&T with 16 out of 30 payments already made ($274 to pay it all off) I tried to trade-in with AT&T and they only offered $97, which I know I can get way more than that.

Is there any way I could sell the phone for maybe $500, then use that to pay off the $274 that's due? If I do that, will the IMEI/ESN still be good and activated with other carriers? Will I still be eligible for an upgrade?

How can I fix my mpow flame Bluetooth headphones?

I've had these headphones for months and they've worked fine. Now they keep disconnecting after three seconds even when I'm playing music etc. They are fully charged. I have an iPhone 6 if that helps. I've tried to reset them but it just turns them on again.

How to disable or lock, shutting down iPhone?

SO I have an iPhone XR. Long Story short, I'm awful at getting up in the morning, had 3 alarms to wake up for work… My mom came in my room and turned my phone completely off so I wouldn't wake up (yes, she is spiteful), and I went to work 1.5 hours late. Boss was pissed and I almost lost my job. Like, I know on Samsung you can put a lock so when you want to shut down the phone, you need to type the passcode… Is there a way I can put a lock like that for shut down, but on my iPhone? Or perhaps disable the ability to shutdown? Yes I know what I'm saying, I rarely even use that feature except when my phone is glitching badly… Which is really are. Otherwise, I don't need the feature. Please lmk, thanks. Tryna prevent this from happening again, so I can have my job!

Added (1). I'm 17… In HS, chill I'm not a 30 year old man who lives in his moms basement lmao

Seller sold me a Blacklisted phone, what can I do?

I bought an iPhone XR at a store may Be about 6 months ago. I should've been on alert when the seller was saying the phone was unlocked, but not to reset the phone. Anyways I moved from att to Metro PCS and while trying to get the SIM card to work, they said that the phone was blacklisted. Which is weird because att took the phone and I was able to use their services. What can I do? Go back to the store? I know that Indian guy will try his best not to return it, especially after 6 months.

Added (1). Should I call the police as well? Onsite if he doesn't want to do anything?

IPhone XS vs IPhone 11?

Would going from the iPhone XS to the regular 11 (not the 11 pro) be an upgrade or a downgrade?

Is this small dialogue grammatically correct? Help ME just 5 lines?

Suzie: Hey, where did you buy that cover?

paul: On Amazon, but i'm not sure.

suzie: Cool. Do you have an iphone, don't you? I'd like a green one for my samsung.

paul: yes i do! You can find one on the web definitely… Anyway, do you want to a movie?

suzie: I have to work tonight.

please, i'm from spain i'm 16 and i'm NOT GOOD in englis help me. Please.
this is for a stupid homework