Hello,
You should be able to run App Game Kit V2 with Yosemite. Currently, the latest Apple software for their Mac lineup is macOS Sierra and they generally don't leave old software lying around for users to download. Assuming your Mac is Late 2009, you can download the latest update from the Mac App Store, if you so choose. Since your computer is older however (and personally I don't like the lower performance I have experienced since updating) you could google OSX Yosemite download and sources such as MacUpdate LLC should come up. From there, you can download the proper file for your computer, open it, and it should be rather easy to install from that point given the guiding pop-ups that prompt you to confirm, etc. Of course, you need to ensure that you are downloading from a reliable source.
[url]{url}[/url]https://play.google.com/store/apps/details?id=games.nicholasshepherd