The thrid partition is not required but recommend.
This entire guide, including creating OSX installer USB is solely for experimental reasons. This guide is just my experience and am sharing it with you guys for educational purposes. If you do follow this guide, please make sure to attain a valid purchased copy of the OSes you plan on installing. I am not responsible for any consequences to your system by following the guide below. This USB drive can be very helpful in urgent situations such as: fixing broken OSX install (chameleon, kext, etc), installing/repairing Windows, or running Live CD of any Linux OS. This guide will explain how to create a USB drive that can be used to install OSX, Windows, and Linux from a single USB drive.
