I have scatter plot and I want to trace the border of that.
for example:
Plot:
and I wanted it traced:
Or at least wanted to know the border points?
Also, is it possible to detect if any point exist on inside or not?
You probably want to look into the literature on Alpha Shapes. They are a generalization of convex hulls and should give you what you want. There's a discussion in this Stack Overflow question about a Python implementation.