Some videos won't play on iphone?

I have an iPhone 5c and a recent problem is when i try to play videos. Often when i press "play" i get the play symbol with a line through it, similar to the no smoking sign. Although some videos will work normally

Can another person see if I accidentally restored from their iPhone backup?

I used to jailbreak iDevices and I had a bunch of other people's iPhone backups stored on my computer/iCloud. I was updating and restoring a personal iPod Touch 4th gen and I accidentally restored from another person's iPhone backup. The screen on my iPod is badly cracked so I couldn't see the name of the backup I had chosen to restore from. (both my name and the other person's name start with the same couple letters, that's all I could see) I went ahead and signed in with my Apple ID on my iPod.

An hour later my mom calls me and said a message came up on her iPhone saying something along the lines of "iMessage on (persons name)'s iPhone is signed in with (my Apple ID)". My mom uses my Apple ID on her iPhone so I'm assuming that's why that message came up. But I immediately did a full data erase and reset on the iPod and set it up as a new iPod.

So my question is, if my mom got that notification, could the other person have gotten that message too? Or does it only apply to the devices signed in with my Apple ID. The other person has their own Apple ID, and I believe they now have an Android phone as well. But I just don't want them to see that message and think I was getting into their stuff and have problems. Although I doubt they even know my Apple ID or even remember I jailbroke their device as this was over 2 years ago, but it still worries me.

How come the iPhone won't pick this up?

<link rel="stylesheet" media="only screen and (min-device-width: 721px)" href="css/styletab.css">
<link rel="stylesheet" media="only screen and (max-device-width: 720px)" href="css/style.css"

It always defaults to styletab.css. Works on android.

Added (1). <link rel="stylesheet" media="only screen and (max-device-width: 720px)" href="css/style.css" >

Can't activate internet with no Wi-Fi?

I got an IPhone 5s yesterday for my 17th. Basically, I'm with Vodafone and brought a freebee. I have unlimited texts, 150 minutes and 250 MG of internet. I tried using Instagram at school, but it wouldn't load. It says 'subscribe to mobile data' or something. My 4G was on, I just want to use the internet:/

What is best to record music on?

So I've been told I'm a good singer and want to record some music to burn onto a CD. So what should I record on to get the most quality? An iPhone, iPad, Laptop, Video Camera, or regular camera? Please help! Thanks!

Added (1). I can't afford to go to a recording studio and I don't want to spend lots of money if I'm not that great. So if you could please not suggest this, that would be great!

How to download songs straight to my iPhone 5c?

So on Friday I got an iPhone 5c for my birthday. And I can't put any music on it using iTunes because my computers broken. So I don't have any music on my phone. What I was going to do is download music using youtube but my iPhone doesn't let me. So my question is how can I download music straight to my phone without any computer? Is there any apps that work? (I've tried a few apps and none of them work)