Chose the "latter one" and you are presented with this..., so more like download OS X after you install Mega.If using a modern browser, it should present 2 buttons: "Download using MegaSync" and "Download using your browser". Choose the latter one and it should work fine.
Early intel versions of Tiger are not available on retail disks. The only way to install it is via the original gray install DVDs.OS X 10.4.6 (Tiger) is the earliest you can install.
OS X 10.6.8 (Snow Leopard) is the latest you can use.
So you have your choice between Tiger, Leopard or Snow Leopard.