Is a two year contract actually two years?

I just recently got a new job that will allow me to splurge a little bit and finally upgrade my phone. I hope to switch from Straight talk over to AT&T so i don't have to continue paying $300+ when I need a new phone. The iphone 6 is about $100 with AT&T s two year contract, and then I'm eligible for an upgrade. Will I be held in that two year contract or would I be able to upgrade earlier to a more recent version? How much does it generally cost to upgrade early?

My sound on Iphone 4 doesn't work?

So a few minutes ago i tried to record one video, and when i play it it didn't have sound but my phone is not on mute and when I play older video it does have sound… Can somebody help me?

IPhone 6s what is this? A glitch or a feature?

From time to time I'll be browsing on Safari or on my messaging app and this happens. Where the app I'm on just moves down and there's a black space covering up the upper part of the phone. Is this some sort of feature or glitch? If it's a feature, what's it for?
This is easily fixable by pressing the home button. IPhone 6s what is this A glitch or a feature - 1

Connecting an iphones internal hard Drive?

My iPhone broke, and unfortunately, it had a lot of pictures from my recent holiday with my family.
The hard drive, however, survived undamaged
Is there any possible way for me to get the information off the phones hard Drive? It was an iPhone 4