Obviously Neutral monsters have a green life bar while hostile enemies have a red one. When attacked their life bar turns red. That much I understand.

But one time I accidently attacked the Wild Saurian in the Stepping and ran. I came back later to find his life bar still red. So I reset my game rather than have such a powerful monster hostile every time I walked by (I only had Vaan and Penelo and at level 15 at the time).

My questions are:

1) Does this apply to any neutral monster that you attack but do not finish off? Like, say, a Cactoid?

2) If I killed the Wild Saurian, would another appear in its place that is hostile or neutral again?