I am little confused, I have diferent closed curves and I want to detect all curves inside each one. Te output should be a tree branch (one branch per closed curve or surface and inside every brach all curves that are inside them).

The result should be like using Region Intersection component, but inside my closed curves could be other opened and/or closed ones, so for this case it does not work.

I think that I am almost near the solution but I am not sure if it is needed to program some code.

Long is the path (and hilly). See attached (the general case: containment in a crv List) - I do hope that you know what a DataTree is (“kinda” a dictionary of Lists - add some " " more).

Thanks both for your solutions. Finally done by extruding Z positive and negative closed curves, joining them, capping holes and using Shape in brep. Using smaller than comparision and cull pattern I get the desired information.