That's so weird, on Youtube every single video sounds perfect. Except for the one I tried to show off because I was showing it in-game. It just sounds completely reversed to me.
If it helps, I had the Turtle Beach PX22 about three years ago from what I remember. That had absolutely no issues aside from well... they aren't exactly durable. Which prompted me to buy Hyper X Cloud II. Now immediately when buying this I could immediently notice that when playing Left 4 Dead 2 that something was wrong (the PX22 didn't have this problem, I've played over 5,000 hours of L4D2 and trust me, I KNOW something is up). It just felt reversed. (I tried support which told me to download the latest firmware. Didn't help at all.) At the time I loved the Cloud II's because the microphone and sound was excellent, so I kept them and just swapped the L channel to R and vice versa using Equalizer APO. Now the game audio worked perfectly for all my games! Except that out of anything game related like Youtube it would just sound reversed. Well, except from the recordings of the videos I DID while these L-R channels were swapped, like this one below:
Go about 3:00 in and you can probably do a test to hear if it's working properly. But I can probably guess that for you guys this one is reversed because of the channel swapping I did. Funny, because it sounds very reasonable to me, I know what's coming and can react to that location.
Now I bought HyperX Cloud Alpha because I wanted this problem to go away (it obviously didn't). My first assumption was the headphones so I just figured to buy another pair (probably shouldn't have brought the same company but the sound feels amazing when it bloody works right, and they're super durable, Cloud II still has zero issues aside from this problem.
Anyway, I'm on a new OS now and I don't have that software, and I'm on a new hard drive. The other one I used isn't connected anymore.
As for your second question, I've muted one side and it still sounds reversed. So if I mute the right channel and all the sound is coming from the left, I can still feel it from the right. And it's vice versa if I mute left and try right, it 'feels' like it's' coming from the left.
Can you suggest any free games I could possibly test? I'm literally broke at the moment and frankly, I don't want to buy games merely for testing. The headset alone set me back £70.
Edit: I just tried my TV, which is attatched through HDMI and that works fine for both in and out of games.