Sorry, good question, can't see any marks. There's so little metal showing it's hard to tell, could be plated, but strictly guessing, ring is 97% stones.
No markings that I can see, so no, not sterling. As for turning your finger green, I've never really worn this ring, so I can't swear to it, sorry. Knowing where it came from I doubt it tho, she loved her rings and bought quality pieces.
I'm so sorry, wasn't around yesterday. I can no longer add pics because it ends so soon, tried but, no go. The sides are kind of ridged, 4 ridges, then smooth, then 4 ridges, and so on. It's actually rather well done. Bad at describing, but I hope it helps! Good luck!