You need some way to tell your OSs that they are not alone and that they can't hog all the resources so, no!Anything that will allow two OSses to run at the same time will be virtualization even if they would call it something else.without using virtualization
Yeah you would need a special BIOS that would divide all the resources from the get go and then boot both "systems"at literally the same time?
I doubt it, unless they are specifically written to coexist and one boots the other as BIOS doesn't keep trying to boot drives once its booted one.