DISCLAIMER: This entry is made merely for educational purposes. Follow this jailbreak guide at your own risk. Note that improper jailbreak procedure can brick your iPhone. This post is subject to imperfections. I suggest you check out other LimeRa1n jailbreak step-by-step guides before proceeding.
Reports have reached us stating that some LimeRa1n jailbroken iPhones are missing Maps, App Store, Calendar and Game Center icons and never regained them even after a restore. Be careful.
Here's how to jailbreak iPhone 4 running 4.1 iOS using GeoHot's LimeRa1n --
1. Make sure you have a Windows PC.
2. Download LimeRa1n on your PC via this link.
3. Connect your iPhone 4 4.1 to your PC via USB
4. Click on LimeRa1n icon on your computer. This will sniff out your connected iPhone 4.
5. Click on Make It Rain banner. This will prompt your device to enter into DFU mode.
6. To enter into DFU mode, just follow instructions on LimeRa1n window;
a. Hold down Home and Power buttons (don't worry if iTunes pops out), until it instructs you to let go of the Power button
b. Enter DFU mode
c. Once it says 'Expoiting...', you can release the Power button. You will see a big LimeRa1n logo on your iPhone's screen.
d. A message will pop up and your jailbreak is done.
7. Turn your unit back on.
8. Click on the LimeRa1n app icon (white rounded square) on your iPhone 4. In LimeRa1n app, tick Cydia and click install.
That's it! Enjoy your jailbroken iPhone 4!