Will Apple take back or repair/replace my iphone 4 if I bought it around Christmas?

I got it around Christmas since my samsung intensity wouldn't hold a charge unless I had the right charger it liked. So I got the iphone 4 for Christmas because my dad wanted to see how id do with a smartphone. But since it came preinstalled with iOS 6.1.2,(Verizon store) I was wondering if it were to malfunction, could I get a new iphone 4? Or would they tell me to buy an entire new phone?

IPhone 5S Fingerprint scanner issue?

I recently got a new iPhone 5S as I lost my previous iPhone 5. Its only been 2 days since I bought the 5S and the fingerprint scanner was working perfectly. However, I synced my 5S with my iPhone 5 backup on my iTunes and now the fingerprint scanner doesn't work? The lock screen also has a "Slide to unlock" thing on the bottom as opposed to the iPhone 5S having nothing there. I should mention that I also updated the phone while syncing to the latest 7.1.1 update. The iPhone 5S Fingerprint scanner settings are all still there but the fingerprint scanner itself does not work, it doesn't even say "Try again". I also already have both my thumbs' fingerprints registered in the settings. What should I do to fix it? Should I reboot the iPhone to factory settings or is it permanently broken?

Why isn't my sound working?

So it was just a sudden problem. I try to put the sound up and it doesn't even show the little picture. But if i go to sounds on the settings it starts working as i click the home button and go to my homescreen it stops. Why?!

My iphone is using way too much data?

My iphone is using an ridiculous amount of data all the sudden. Ten days into my billing cycle I got a text saying I've used the entire 5 gigs of data and they were adding an additional gig for $10. About five hours later, I got another text saying I'd used 75% of that. I got another about 10 hours later saying I'd used 100%. I'm not doing anything different that I can tell. When I'm home, which is most of the time, it is on my home internet (I checked and it's on the right setting). The network sharing is off. I've been closing my apps.

Does anyone have any ideas?

Who do I call to figure this out? AT&T? The apple store?

Can I activate an iCloud locked iPhone?

Bought off ebay. The buyer said I shouldn't have any problems with it but I need other peoples opinions. The iPhone is iCloud locked. Is it still able to be activated. If so, what are problems I may encounter.

For some reason, Itunes won't add my video?

I have a video on my computer and want it on my iphone. It's.MP4 format, and I looked at it properties. I unchecked the "Read Only" box, but iTunes still wouldn't add it. I tried opening it to play in iTunes, and it wouldn't even open the video. I tried to add it by going to "File" as well as dragging it.