Currently Being ModeratedNov 26, 2012 2:51 PM (in response to tonyibrahim)
When you update from your computer, you'll be asked if you want to setup as new or with your backup. If you select backup, it will restore all your apps and messages back on.
If you update OTA, you won't be asked and you won't lose anything. That being said, always backup before updating any device.
Currently Being ModeratedNov 26, 2012 2:56 PM (in response to tonyibrahim)
No. Since you're updating from iOS 4 to iOS 6, you may have to restore the iPhone after updating.
So, just backup your iPhone before updating.