When you update your Iphone, does your data get erased?

Molly

My friend wants to updated her iphone 4 to the latest software, she wanted to know if the data gets erased?

Ash

No it doesn't as long as you've synced your idevice to your computer before

Cristina

DON'T update! It sucks. You can't send picture messages & overall it sucks. But no it doesn't delete your data

My iPhone data got erased So, a couple of minutes ago, I updated my iPhone 4s to iOS 6.1 and it told me that I *needed* to restore my phone for the update to work. I did and after I turned on my phone, EVERYTHING was deleted. My messages, pictures, contacts, everything on it. How do I get all that data back?
IPhone 5 iOS 7 fail and stuck on recovery mode, don't want data to be erased? I tried updating my iPhone 5 to iOS 7 without Dev.account. It failed and now I'm stuck on Recovery Mode. I want to restore and downgrade, but I don't wanna lose all my media like photos, videos and apps. Any solution?
If you update your iPhone 4S to 6.0.1 through Wi-Fi, does it erase all your data? I have updated to 6.0 before on my laptop in iTunes, but strangely it didn't erase all my data, so I didn't have to back up. I didn't see it automatically back up during the process of updating, so I was wondering if it would erase all my iPhone data if I updated it through Wi-Fi. A few months before, when I updated to 5.1.1 it erased all my data. I'm not sure if Apple did anything to 6.0 that made it not erase my data…
If I delete a message from my iPhone, does it erased completely? What I mean is, let's say I texted the wrong person and I want to get rid of it, so I delete it. Does this make the sent message delete it on the other persons text history as well? (that the other person won't be able to see it anymore).