How to Uninstall OS X 10.10 Yosemite
So, you installed the public beta of OS X 10.10 Yosemite and now want to uninstall it?
It's simple. Just reboot and hold down the Option key, then select the partition/drive where you have OS X Mavericks installed. Press Enter and you're done!
Because you didn't really install a beta OS on your main partition/drive, right? Right?!