I can’t find where to download the patch to upgrade from version 1.1.2 to version 1.2.0 (polacolour update). The oldest version seems to be in the 1.2.0c in the download list of the game. I can't upgrade to the Kenya update without polacolour update. How find this update if it isn't in the download list ?

You don't need to install every hotfix since v1.1.2 to get the keyna update. You can just download the installer for v1.3.0. That's probably going to take less bandwidth too.

EDIT: If you're worried that a fresh install might mess up something, just rename your current installation folder to "artofrally.old" or something like that.