I want to share my experience with my dear mates (how to downgrade iphone 3gs)
but do all @ ur own risk, I'm not responsible for any thing! Just read everything carefully & do it if u want!!!
Important it will not downgrade your modem
Remember if you have saved backup of shsh blobs then you can downgrade in any version as you can see in cydia’s home screen.
But if you don’t have any backup saved then no problem at least you can downgrade from 4.3.1 4.3 to 4.1 old boot or new, no problem just follow up the step by step guide.
You should have
1.tinyumbrella-4.30.05 download it from here
http://cache.firmwareumbrella.com/do...la-4.30.05.exe
2. recboot 1.1 download it here
RecBoot_v1.1_Win.zip
3. itune 10.2.0.34 download it here
Apple - iTunes - Download iTunes Now
4. Greenpois0n RC6 Final version download here
http://cache.greenpois0n.com/dl/gp_win_rc6_final.zip
5. Redsn0w 96rc8 download here
redsn0w_win_0.9.6rc8.zip - 4shared.com - online file sharing and storage - download
How to :::…
1. connect your iphone 3Gs to pc open tinyumberela click save shsh & wait until it done
2. now you will see in Genral tab iphone 3gs 4.1(9b443 etc) but if you saved already then you can see more ver to downgrade
3. now click one of them eg 4.1 & click “Start Tss Server” button
4. and open itune 10.2.0.34 click restore by pressing shift key point to 4.1 & until you get error 1013 1015 etc. that’s normal no problem
5. now close itune open recboot 1.1 & click exit recovery
6. now you are in emergency mode use any sim card if you have factory unlocked device to activate & unlock or use redsn0w to jailbreak n ultras0w to unlock
for 4g is the same way but you can downgrade to maximum 4.3.1 4.3 to 4.2.1 (if you have not saved shsh already) after error 1015 etc. use gp_win_rc6_final to bring it emergency mode now if you have factory unlocked, unlock n activate it first and if not factory unlocked use redsnow to install cydia use ultrasn0w to unlock
I did many 3gs old boot new boot and 4g too, you can get help any time i'm ready my dear mates
final step thats very important click thank button if you like my post
regards