I have formatted a usb drive guid partition and installed Yosemite from another mac. When booting, the USB is showing as an option to install yosemite. When I select this and try to install I immediately get a prohibited sign. I also booted normally (el capitan) and selected the usb from the desktop and was given an error "the copy of the install os x application to old to be opened on this os x. Any ideas on how to erase el capitan and install yosemite??
Mac that I'm attempting install on.. -started with el capitan on it -el capitan has been updated once