Mac multiboot flash drive
The Early 2015 MacBook Air can not boot anything earlier than 10.10.2. So anything earlier than Yosemite definitely don't work on that machine. As to why Yosemite doesn't work you need to make sure you're not installing 10.10 or 10.10.1. Just re-download the Yosemite installer from the App Store it will give you the most recent to version of Yosemite.