Upgrading the iphone 3g(2.2) to the newest version

[Prophanus2010]

I know this is nothing new here in the forum but it is for me. I've read the how to's and am now a litle familiar with the specific vocabulary such as jailbreaking and unlocking. but i still have some doubts. id apreciate if anyone could help out:

the case:
i got an iphone 3g runing 2.2. i bought it unlocked. i has installer, and cydia. it works very well on my network here in brazil under any carrier.

questions:
1. Can i upgrade directly from 2.2 to the lastest version? if so, which version is the latest version that runs on the 3G?

2. Since it is already unlocked and jailbroken and works well do i have to do these steps again? cant i simply " update the software "(i know it cant be done via itunes update) .

3. if so, what is the correct order to do it? do i unlock then jailbreak or the other way around?

4. is there any risk for me to do this update from 2.2 to the latest?

5. since the original iphone is not made to work in brazil, which of the necessary steps make it possible to use it here? which software installed " tells" the phone which network works and how does it know the carrier's logo as it appears in the upper service bar?

ps.:
i am noob about updating my software version since its the first time i do it.
i use a mac
and THANK YOU VERY MUCH

 

[daveb1983]

Ok, yes you can upgrade to the newest firmware, you will always be able to do this free via itunes. the newest version is 3.1.2.
Unless your phone is factory unlocked (and its not likely to be if its jailbroken), if you upgrade the firmware via itunes you will lose both your jailbreak and your unlock, but thats does not mean you cant get them back. there is no other way you can upgrade firmware other than using iTunes.
Also most of the jailbroken apps you have now will no longer work on the new firmware so you will need to download new versions of them, this may take some time so think carfully before doing it.
If you really want to do this you will need to sync with itunes, restore and update the phone, this will upgrade your firmware.
your phone will no longer be unlocked or jailbroken
You will need to run blackra1n RC3 (mac version) to jailbreak, once this is done you will have the blackra1n app on your phone.
Open it and install cydia, you can use this to download all your new apps/tweaks
Also in the blackra1n app is the sn0w app, this can unlock any 3G phone to use with any SIM.
This is quite an easy job and i would ordinalrily recommend anyone to do it but considering your phone works well as it is it may be best to leave it.
With you not having a legitimate SIM and doing a major FW upgrade you may lose a lot of apps you cant get back, and if you encounter problems you may have a phone that you cant use.
However the 3.1.2 firware opens up the door to loads of really nice apps/tweaks from cydia
if you do try it and it doesnt work you can always restore and try again
Its up to you
Hope this helps