Is my Straight Talk iPhone 5C unlocked?

So, I bought an iPhone 5C (green-if it matters) from Walmart.com about 3-4 months ago. Now, however, I'm realizing that I really don't like Straight Talk. I have poor service in my area and seldom have service. My question is, can I have my iPhone switched over to a new cell phone provider (Verizon, AT&T, etc.)? I paid full price for my iPhone so is it unlocked? If not, how do I get around to doing that? What is GSM? Is my cell phone GSM? I understand that it has something to do with unlocking phones and transferring sim cards, right?
Any help is greatly appreciated!

Do new iPhones have all 8GB or is some already used up?

Updating my iPhone always takes up a lot of space… When you get a new iPhone do you have all 8 gigs (or whatever it is), or is some space already used? (like for the apps you can't get rid of or whatever? My iPhone is 8GB but I only have 6.5 possible to use in usage… (I've already used 6.5/6.5 lol)

How safe is Private photo vault?

I had a Private photo vault app on my iphone and I had very private photos in it. I'm very concerned now about it's safety and privacy. Who can see my photos in my Private photo vault app and are my photos sent to Private photo vault servers. Can makers of Private photo vault app see my photos? Thanks for your answers! It's very important to me!

IPhone 5 is continuously restarting?

It wouldn't charge last night, so it died the next day. I thought it was the charger at first, so I borrowed one from a friend. So today I plugged it in and then it starts restarting like crazy. The apple logo comes up, disappears, then comes back on again. THAT ONLY HAPPENS WHEN ITS PLUGGED IN. When I unplugged it, it won't even turn on. I have tried restarting it by pressing the home and power buttons but nothing happened. I also plugged it into my computer and still nothing. I have had the same battery for 2 years, do you think that may be the problem? The obvious problem may be that it got wet. I don't know for sure though. I checked the water indicator and it wasn't red, but my phone was a little wet when I got it back. I went into the pool for a while and left my phone on a chair, and when I came back it was wet. My dad may have sat on it or spilled something on it, but I don't know.

What programming language should I learn?

I already know a lot of python/pygame.

I want to learn a language which will give me a broad understanding of programming, and one I can use the most, and is most useful in general, as I find you can really do much in Python…(does anyone else find that?)

I also want to make apps. I only have an Android, so I don't have an iPhone, so I think I'd have to make Android apps…

Any advice? Can you recommend a language?

If it makes any difference… I'm 17:3 i did computing AS level.