Note: the game is already free on Steam itself; however, it's only a free-to-play license. By getting it from Square Enix, you get the retail license - basically the same game, but it gives +1 to your total games (which means more progress for the Games Collector badge).
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@ DanelSonic123: My instruction post probably wasn´t the best written one, but almost everyone understands what I wanted to say. Suggestions for improvement are welcome.
The only exception was for the Half Life Series. Every Half Life Game was time limited Free2Play for around 5 months I guess.
Actually I got a thought I want to share: Is this thread the cause for all this trouble with the spammers?
The game names/game links are, especially in the time-frame from when the games are free, somewhat a target for bots.