Oh okay now I understand. Basically you're asking if it's okay to download a game you already own via bittorrent so you can play the older version of it.
Well every Game publisher will tell you this is illegal, however that law is always over ruled by your countries law.
For example, I am swiss and here in Switzerland we can legally download torrents that contain copyrighted material, and it's not against the law, (the use of copy righted material again is another law) however uploading copyrighted material is against the law.
You would really need to know your own countries law.
That being said, downloading a game you already own, is not a big deal.