Here we posting steps for Activating ,jailbreaking and unlock iPhone 3GS with iOS 6.1.2.Try it 100% works..
Jailbreak your iPhone:
Steps- Restore iphone 3GS with latest version iOS 6.1.2 download firmware iPhone2,1_6.1.2_10B146_Restore.ipsw file (Download here..)
- After restore your iPhone will be Activation Mode
- Download redsn0w_win_0.9.15b3
- Run redsn0w_win_0.9.15b3 as Administrator.
- Click on Extras > Select IPSW > Select iPhone2,1_6.0_10A403_Restore file (Download here..)
- Then Click on Back and then Click on Jailbreak
- Reboot your device then Next button willbe Highlited then put on DFU mode and follow the redsn0w instructions..After reboot you phone will be activated Successfully
- Download evasi0n-win-1.5.1 (Download here..) and Run then click on Jailbreak (for un tethered jailbreak) follow evasi0n instructions
- Your iPhone is successfully Jailbreaked
Unlock your iPhone:
Steps- Download Ultrasnow 1.2.8.zip and itools
- Launch itools then go var/root/Media/Cydia/AutoInstall (if cydia and Auto install not there create a folder with above names)
- Place the DEB files from Ultrasnow 1.2.8 unzipped folder.
- Reboot your device normally.
- Done your phone will be unlocked.

