Is there a difference? Icloud unlock & factory unlock?

I've never had an iPhone, what's the difference in factory unlock & icloud? I've seen something about original owners, is it impossible for me to get an unlocked iPhone and simply make a new account and place a sim card inside?

How to keep iPhone from sending iMessage text?

I have an iphone 4s with the newest ios 7. I had a contact that had an iphone as well. Now, he doesn't have an iphone he switched to a galaxy s 4. So when I receive his text its a regular text. When I try to reply it still sends as imessage and says 'delivered'. I've tried holding on the message hoping for the 'send as text' option to pop up but nothing. I've deleted the contact and then added him again but still sends text via imessage. Tried resetting phone and nothing as well. Tried changing his number from 'mobile' to 'iphone' and back to 'mobile' and nothing. Any help would be appreciated. (apple makes everything difficult)

Is 2.5 gigabytes and 500 megabytes enough?

Well I'm a teenager so of course I'm going to use the phone a lot. I use the internet a lot and FaceTime a lot. I take pictures too. I'm also starting to like watching videos a lot. ( I can stop doing that though if it's going to take my megabytes away or whatever they're called )
My moms going to put me in the family plan with my dad and brother ( we switched to tmobile ). I'm trading in my aunts iPhone 4S for the new iphone 5c. I have unlimited call, texting, web but I have 500 mg and 2.5 gb. I don't know if that's good enough for me. I use the phone a lot and I don't want to overuse the new phone my moms getting me because I don't want her to pay a lot because I wasted all my mg.
I tried researching all this but everyone's saying different things. Please help me. Thank you! I'm not good at this.
Also, if I use wii, will it still take away my megabytes or gigabytes? Like if I'm at home using my phone with Wi-Fi will it take away mg or gb? Is cellular data the same as Wi-Fi?

Iphone camera only works in camera app, not any other apps

I have an iphone 5, and the camera shutter won't open on any apps other than the camera app itself. It does not work in Facebook app, facetime, kik, or anything else. Apparently, my iphone was taken into some repair place to make that happen. And I NEED a fix for this, it is not jailbroken, and has IOS 7 on it.

How to put the music i downloaded on my iphone?

My music i downloaded on my laptop won't sync to my iPhone 5 on iTunes. I downloaded free music from youtube using http://www.youtube-mp3.org (youtube converter) and and the music i downloaded is on my iTunes account on my laptop but when i plug my phone into my laptop the songs won't show up on my phone and its showing a little circle on iTunes next to the songs i downloaded. Should i call ATT? Or Apple? I need help please! -i attatched a picture of what the circles look like when it says there on my phone