How to make the songs and playlists the same on my iphone as on the computer?

I have songs and playlists on both my computer and iphone, but they differ slightly, and they are missing some and some have some additional playlists. I want to delete all the playlists (and songs maybe?) on my phone, and sync everything from computer exactly onto my iphone. How do I do that? I have tried several times and have failed. Also, how do I keep from songs appearing twice on my iphone?

BTW, it's itunes I'm using. And more importantly, I started downloading songs from youtube, and transfer them over to my itunes library. For some reason, some of these songs didn't even appear on my phone.

Does skipping updates in ios7 matter?

I recently (like a week ago) got an iphone 5s. When i bought it, it was on ios 7.0 and i immediately updated it to the most recent update - ios 7.0.6
does it matter that i skipped all the updates inbetween ios 7 and ios 7.0.6? My iphone has been really laggy and when it multitasks the screens always take a second to re-align it's self and i haven't seen this be an issue on anyone else's phone. I'm just worried because i bought it like a week ago and it's a 5S so i assumed it would be the best out there, but my phone seems to be having issues i haven't seen on others

Added (1). how do i get every update?

How to make photos that i screenshot full sized on iphone 5?

I got the new iphone and i'm screenshotting all my photos through instagram and if i crop it the picture is cut in half in a box shape(almost as if i took a picture with the square setting in the camera) but i really hate that! Is there an app or something where i can make it full sized, where the picture reaches top to bottom

Will i loose all my data in this iphone sync?

So i got the iphone 5s for christmas and its my first time plugging it into my computer, my options are backing it up as a phone last backed up from 2012 or set up as new iphone will setting up as a new phone erase all my current data?!

How to sneak an iPhone 5c through metal detectors?

I have an iPhone 5c, and I was wondering how I can sneak it through the metal detectors. Some girls sneak it in by putting it in their bras. I go to this really shitty school and they check EVERYTHING. Even our lunches ( on occasion ). I can't sneak it in through boots/shoes because they're starting to make us take them off. It's kind of important for me to bring my phone to school, just in case I need to contact my mom or something. 5c's seem to be plastic, but I'm not sure. A lot of my friends have the same kind of phone and sneak theirs in. I'd just really like to find out how I can do this without getting caught. And again, I can't sneak it in a lunch, or my shoes, or my bra. I don't want anything such as it's school and you should do your work. I don't use my phone during school. I'd only like it for emergencies. So serious answers only!

What is in an iPhone charger cable?

I took apart my broken iPhone 4 charger cable and am curious about my findings. The first layer is the visible outer white plastic covering. Than there seems to be some sort of finely woven metal mesh. Under that of course, are the wires that care power to the phone. What is the woven mesh for, and what are the fine hairs in with the wires?