Thanks, that helped!
P.S. Yes, I meant a stone without any card.
1) Yes. "active the text" is a mistake - it's a bad translation.
2) I'm not sure what you mean by "on an empty" - a stone without any cards?
It's played next to an unclaimed stone, and does not count as one of the 3 cards. You can play it even if there are no cards "fighting" for it yet.