There should be some kind of code or key to unlock the game, and you have to enter that, and also make sure you've completely uninstalled the trial (check Add/Remove Prgrams and also, delete the shortcuts, those might have an effect as well)
Hope I helped. I dont know if you work on a mac or PC, and ive never worked on a mac (Yes, its true~) so I dunno if theres any difference with the name for "Add/Remove Programs" But I still hope I can help.

It's a matter of compatibility, all you need to do is use the Mac version of the game and it should work fine. however if there is no mac version of a game on the website u use, check other websites, someone's bound to have it. I'm not a professional at these tech things so i can't give a better explanaition that that. However i do know that mac computers can't read the same types of files as PCs can so they have to create mac games using a different file/format or whatever, so ya. thats all i can do to help but i hope i gave u at least a hint of advice.