You only get one serial. Or at least, any serials you do get are generated from the same seed and thus count as the same one.

Just an fyi. I do not intend(if the cd version has a different serial number than the downloaded version) to then sell the cd version and keep playing(thus almost getting the game for free). If anything, I will sell the cd version along with my login info(if the cd version and the DL version are the same) and STOP PLAYING(if i get bored or need the money). If the two version have diff. serial numbers. I will simply sell the cd version and again, STOP PLAYING.

Reselling the game after registering the serial is in violation of the EULA, and Stardock will not provide any support to wheover you sell it to.

FYI, the first "foreign" copy that you bought online was 99% likely a pirate bootleg.

Because the bootlegging factories are in Russia and/or east Asia, and the games they copy are intended for distribution in those areas (where the authorities really don't care about piracy). Some people buy up large amounts of them for dirt cheap and sell them at a profit to customers in the US.

These are often marked on eBay as "IMPORT EDITION" and say they are used copies (to cover their rears on the fact that the serial won't work, and in fact is sometimes just random gibberish--in some cases for GC2 it hasn't even been the right length). they often specifically state that the game is not pirated (if it isn't, why bring it up?). Also, the 'foreign language' bit provides a convenient excuse for excluding the documentation and other materials when selling it back into the US (the less they give you, the less clues you get that it's pirated). Combine some or all of these clues with strangely dirt cheap prices (usually less than $10), and you've got a dead giveaway that it's pirated.

As of right now most of the GC2 auctions on ebay appear to be legitimate (though mostly used, and thus unsupported) UK copies of the game. Just last week though there were at least nine pirate auctions going in the search results for galactic civilizations 2.