My iPhone 4 is broken and I don't know?

I have an iPhone 4 (not the 4S).It's fairly new, I got it in April of 2013. The other day I dropped it on the bottom of the phone and the entire back of it popped off. At the bottom two hooks snapped off and allowed the back to come off. My phone will not connect to my service provider but connects to Cellular Data. It won't allow me connect to wireless internet either. Anyone have any suggestions. Or tell me how much a repair/replacement will be? Or how long repairs will take before I get it back. The back doesn't want to stay onto the phone either.

What should I use to loosen a tight screw?

I want to replace my iphone 4 screen (because it's cracked) and the instructions say to take out lke 10 screws. I got 9/10 and the last one is stuck. Whenever I google it, it tells me to use WD40. I don't know what that is or where to get it and I need a solution as quick as possible. I don't want to ruin my phone btw.

Added (1). I don't have time to go and buy it, so is there any other solution?

Should I bring my iphone to summer camp?

I'm going to FFA camp next week, and I was wondering if I should. I looked at all the guidelines but it doing mention it. My dad is worried I might misplace it, and I just got it earlier this month. What should I do? I really want to bring it.

Why won't my iphone 4 send text messages to one of my contacts?

My iphone 4 is in perfect working condition and it successfully receives and sends text messages to all my contacts except for one. I had been texting that one contact all day, but around midnight, my phone kept saying, "messge send failure" with a little "!" beside the text every time i tried to reply. Why is this? It's been around fifteen hours and it still won't allow me to send messages to that one contact.

Great Photo editing apps for Instagram?

Ok well I wouldn't say I'm ugly, but I wouldn't put a pic on instagram without editing it. Can you become photogenic? Or is that something you born with? Please comment with best android AND iPhone apps, because I have a galaxy s3 phone and an iPod 5. I already use picsart and phot grid, anymore? Please comment! My pics on instagram are not ugly, I just want more better looking editing for MORE likes! I have over a thousand followers, but only get like 25 likes on a pic:/ please just help me with photo editing apps! You can also comment our instagram name and ill follow u.

Anywhere that replaces the bottom back part of the iPhone 5?

I have been so careful with my iPhone 5 but I dropped it once even with a case on and it cracked the back bottom shiny part of the iPhone, I don't really want to do it myself as I don't want to risk it, does anyone know anywhere that will repair/replace for me for not too expensive?