How to get parents' trust and phone back?

I'm a freshman and in April I got my phone taken for numerous reasons. It's now December and I really want it back. Everytime i mention it they shut down the conversation and they are really strict. Now, I want a new iphone but in order for that to happen, I'm going to need to earn their trust and get my phone back. Keep in mind, I tried the whole do chores thing, and tried talking to them. What should I do?

Why is my Facebook logged into multiple devices?

I was just randomly checking my account settings and was looking at devices that are logged onto my Facebook and it shows multiple devices, all from iphone 7plus which is what I have. This might be a stupid question, but wouldn't it just say iphone 7plus once if my phone is the only one logged onto Facebook? On my account settings, it shows 5 other iPhone 7 plus logged into my messenger, one location says it was in San Francisco but I was no where near San Francisco (but I do live about 45 minutes away from SF). Does this mean someone else is using my Facebook? I'm just really confused.

What is Other in IPhone storage?

My IPhone 6s is almost full, and when I look to see what is on it, it says over half is full of "Other." What is it? It's not apps or music or photos. I looked online and it said to clear internet browser history and that did nothing. Could it be one of my apps? I just want it gone.

Should I get an iPhone in the UK or US?

Basically this Christmas I would like to buy an iPhone 7. Then I remembered that my aunt from NYC was coming and I wondered whether I should get her to buy me one there. In the UK, an iPhone 7 is £549 and in the US it's $549 (that's £408.66). So should I get an iPhone from the US? I'm aware there's a tax added when you buy it in the US so my aunt lives roughly in soho but I don't know what the tax rate is there? Also is there any other difficulties in getting it here like will it work with UK networks? What difficulties will happen getting it out of the US and in to the UK? Etc