Probably this has been asked before, but I couldn't find anything.
1- Does Lava affect Stones? Core rules for Lava talk about figures, which Stones are not, so I'm not sure if they would be defeated by ending their activations there.
2- Can a Fire Breath be traced through a Stone? And if a Stone is attacked, can the Fire Breath be traced from it? Stones are obstacles, and as per rules, spaces cannot be counted through them, so I don't know.