Is there a difference in iPhone body?

This may sound like a really dumb question, but I have reason for my suspicion.
My mom had a black 16gig iPhone 4. The family upgraded phones and in it I got a white 8gig iPhone 4. My mom gave me one of her cases and it fits perfectly, but the silencer switch and volume buttons are a little off.
When my brother and I went to Best Buy, some of the cases said specifically for iPhone 4 16gig and 32gig. Others said iPhone 4.
Is there a difference at all?

My iphone sound isn't working?

I have the iphone 5 and have for the last few months and never has this happened before. My music says its playing yet i can't hear anything and i can't hear anything when i'm on the phone to someone, yet when my phone rings, my ringtone plays fine. I don't understand what's happening? Its not on silent or anything and i haven't dropped it. I would very much appreciate your help!

Is it better to have more or less pixels per inch for better clarity?

I'm not sure if that makes sense or if I have asked it correctly. What I mean is if the Iphone 5 has 326 PPI and a HTC has for instance 440 PPI which one would be better?

Added (1). So would that mean the pixels would be larger on a computer screen with retina display or would they have to be smaller?

Does a otterbox really work?

I'm thinking about getting either a iPhone 4 or 4s. I tend to drop my phone sometimes & I was wondering does a otterbox really work? If I was to drop it would my screen crack(with the case on)? Just until I could get a life proof case.

IPhone 4S speakers not working? - 1

I've been out on the snow so my phone may have got a BIT wet… When I press the volume keys on left hand side of phone it just says ringer and no sign of controlling any volume, when I open music the music doesn't play and once again the volume bar isn't there. However voice memos work out loud but I think that's it. I have restarted my phone and still the same issues.

If I cut my sim into a micro sim will my iPhone 4S work fully?

I currently have a Blackberry Bold 9900 which is in contract but am getting a iPhone 4S. But the sim in a blackberry is not the right sort for the iPhone 4S, so if I bought a 'micro sim cutter' and cut the sim from my blackberry and put it into a 4S, would the iPhone work fully like apps, siri etc and I get all my minutes, data and calls etc…