The iphone will be restored using the last backup so your info will be saved and it will still be unlocked.
Yes, by plugging the iphone into your computer and updating the software on it using itunes.
you dont
Yes. If you update your iPhone's software using iTunes it will lock your iPhone again. You will then need to unlock it again.
Yes, if you restore your iPod or iPhone on iTunes it will delete Cydia. The restore function on iTunes restores your iPod or iPhone to its previous settings.
Yes,If u have Bought it in itunes u can log in and redownload it at itunes on pc or u idevice
If you unlocked your iPhone it is easy to access apps store all you need is a account to download thinks from there,if you jail braked your iPhone you may download thinks through cydia only .
Itunes on the iPhone is preinstalled.
Yes, you can "Undo" a Jailbreak, by going into iTunes and Restoring your iPod Touch, or iPhone.
Sync your iPhone to iTunes on our computer
Apple only allows us to import iTunes to iPhone, not add iPhone to iTunes library. If you want to add your files from iPhone to iTunes, you have to use a third party program.
Yes. there is no problem doing this. All you need is an itunes account. the appstore app will work fine.
no you cannot use ipod and iphone apps on itunes, but you can buy the apps on itunes and put them on your ipod and iphone