Installation on older Mac OS X versions

Thanks again, puzzlezaddict !! So there's no solution to it? Can I install a disc version of IP if I can find it as second-hand in ebay or similar? Would a disc version work even if the registration code has already been used by the first owner? Would it turn my installation into a disc-required version? (I mean, I remember that quite a few years ago, the Sims2 DVD was required to be on the drive for the Sims2 to start, so I'm wondering if something similar could happen to my Sims3 installation if the Base and Ambitions was a digital download and then I install IP as disc version).