I have been using iPhone 3GS for almost 3 years now, and the phone has got pretty slow. I understand that there are many reasons for the phone getting slow, but I want to try to improve its performance, even if it is by a meagre amount, by formatting it completely and installing the latest iOS it can support, i.e. 6.x.x.
However, I don't want to lose important data like messages, contacts, notes, internet/network settings, etc. by doing a format and clean install. I have the latest iTunes installed, and would prefer iTunes for this process. I know how to update iOS using iTunes and restore from backup, but I am not sure about format + clean install AND then restore all the important data.
Can anyone please advice me how should I do this task?