You can't upgrade your iOS on your iPhone without loosing some of your jailbreak. There are some feature (like battery percentage) that are farther in the software and will stay, but Cydia along with most (if not all) of your jailbreak apps will be taken off. You can backup your apps using RockApp, but you loose your data within that app. If/when you update your iPhone you can jailbreak it with RedSn0w then download RockApp again from Cydia and get your apps back, but you may just want to hold off on updating and just stick with what you have.
No the data won't delete from the iPhone unless you reset everything
No possible way
You can't delete the Nike app because it comes with the iphone.
Jailbroken and are not located in the US.
If you are trying to delete an app without an x, it means that you cannot delete it. The apps that cant be deleted are the ones that came preinstalled on your iphone. In other words, apps that are preinstalled cant be deleted while apps that you install can be.
you hit the delete button
they are two different things! an itouch is basically everything that the iphone is without the phone. you can also install most of the apps that you can on an iphone on an itouch
No
No
No
delete it
The easiest and fastest way to delete 5,000 old emails from your iPhone S4 is to just delete the email account.