This is a full guide on how to read iPhone passcode with Gecko iPhone toolkit, here you will get step by step guide with pictures and screenshots so that you can remove your iPhone passcode without restoring it. Gecko iPhone toolkit is easy to use but for people who are using for first time, not that easy. As you all know this tool works on A4 or lower device from this previous post, so this method will work upto iPhone 4.
I used my iPhone 4 to demonstrate this process, so i used firmware for iPhone 4 (3,1) if you are trying on iPhone 3GS you should download firmware for iPhone 3GS ios 5.0.1 no matter how higher your firmware is, i.e if your device is running on iOs 6 or iOs 7 you will need to select iOs 5.0.1 firmware while you boot in first step. Below are the steps you have to follow.