A suggestion... Be clear what product you're stating the version of. You talk about iTunes running 10.7, but you're actually (I think) speaking of OSX 10.7 vs 10.10 (but since you don't even say you're running a Mac, it's hard to tell). There is also a version of iTunes 10.7.
As far as running multiple version of OSX on your mac, I have no idea. No use for that sh*t. Don't know why you'd want to. Just put the latest version on, and it should be backwards compatible. But since you (again) don't state which MacBook you have... They made more than a few models, I think.
C