I'm trying to create a dual boot Mac that has 10.6.8 Snow Leopard on one partition, and then 10.7,8,9,etc., on a second partition. Is this possible?

I'm also wondering about how sometimes an OS upgrade comes with a required Firmware Update to install first. So lets say I have a machine that I want to boot multiple OSX versions on, will the Firmware update for 'El Capitan' (if there is one) break the machines ability to boot into an earlier version, say Snow Leopard?