Agreed, and my guess is, all others will be copies of the first ruins found.
I don't think so, In fact, the copy we found, is either a mistake by a dev, or an actual copy instead of another ruin.
If its an actual copy, that means there are a lot more ruins out there, more than we need for the puzzle, we may be dealing with more than one set of ruins in every planet, we just haven't found them yet.
I refuse to count the second ruin as anything different than the first one we found, copy pasted to the last detail, even the data it gives, so, I believe that there are 5 different ruins, and multiple copies of each. -or- 4 different ruins without copies, but the fifth was a screw up by the devs.