IPhone 5 used 50% of prorated data?

So I've had my iPhone for a few days and it said I've uses 50% of prorated data and I have until June 3rd til renuid. What does this mean? And the Wi-Fi right now isn't working so i'm using LTE. Also if it's from LTE does it effect it if I text?

Are photo lock apps trusted? (iPhone application)?

I want to store family photos and some embarrassing memories in a private photo lock app.
I heard "ePhotoChest" is good photo lock application on iPhone.
But are these photo lock apps to be trusted?
Can they steal your private pictures since they made the app?
Or is it safe to use?
Explain please, I'm really curious

Lock iphone music to always on?

I want to lock my iPhone 4S so that the volume and music selection can't be changed from the home screen even when the pass code is on. Is there anyway to do this?

Iphone 4 network settings problem?

Basically after updating my iphone 4 to ios 6.1.3 network simply isn't in the settings/general can anybody help i'm on giffgaff so need to input the settings but i can't find then. I go into settings-general and there's no network or celluar options anywhere.