Help iPhone 7 plus Jet black owners?

Well, i bought iPhone 7 plus 2 weeks ago and since then i kept it in flip cover as apple mentioned that its easily scratchable. And today i removed its cover and saw from backside's upper and bottom side (antenna area's) shine is gone and there's some thing which can't be cleaned and easily visible and not looking nice. I don't know what to call it but there's some dirt i guess or it looks as if paint is removed so my question is how to get and maintain the shine of jet black color? I like to keep my phone clean and never had any problem before with any phone. I feel like I shouldn't have chosen this color because this happens in 2 weeks (even in its case) and what will happen in near future and no one will buy it when i try to sell it to buy another phone even if someone will buy but they won't give me good price. Sorry for my bad grammar since my language is not English i tried my best to explain it to you and now expect you to respect me and give me a better solution. Kindly reply and, Thanks in advance.

Am I spoiled? Srry for bragging?

My friends keeps calling me spoiled and it's getting annoying. I don't brag about it but if we talk about what we're doing for our bday or what we got she starts calling me spoiled. I'm thankful for what I get.
This is what my family has
-Toyota Sienna
-A House somewhere in the Bay Area with 7 bedrooms, 2 bathrooms, cabin in the backyard, and 2 stories.
I have
-had 7 phones and now iPhone 6s
-my parents put $300/week in my bank account
-Solo Wireless Beats (space gray)
-use to have ukulele lessons, swimming lessons, karate, dancing lessons of tap, lyrical, ballet and hip hop, piano lessons.
-use to have maids
-use to go to a private school but now public school
-clothes from VS Pink, Hollister, Forever 21, Abercrombie, H&M, Justice, and Old Navy
-I have an Xbox 360, Wii U
-Piano, ukuelele
-2 Uggs, Adidas, Nikes Huraches, 2 Nikes, MK Shoes
-3 AG dolls
-2 iPads one a mini and other an air
-2 laptops one a MacBook and the other a Sony via
-go to a theme park/vacation every year
-mostly eat in a restaurant everywhere week
-I have tons of phone case
-For my bday I normally get 2 cakes
-Last year for my bday I went to Disneyland this year for my bday I'm going on a Disney Cruise
-I've been on a Plane 3 times
-have braces for $5000 and also glasses

So am I spoiled?

Can I trade in my iPhone 4 at the Apple Store and get money off it?

I want to get the rose gold iPhone SE in 64 GB. I'm going to start babysitting over the summer so hopefully by the time high school starts I will have a working iPhone. If my parents got me a phone it would be a Samsung but I hate Samsung. They say apple is too expensive and if I want an iPhone I have to get it with my own money. The iPhone 4 that I was talking about hasn't had a SIM, so it basically is an iPod. Do you guys know if I can trade it in at apple and get money for an iPhone SE?