Maha,,, This seems to work much better if you right click on the spline and select "Simplify Spline". Before I did that I made a copy of the spline in a new sketch then removed the on edge relation. After simplifying your spline I compared the two and could not see a difference. The coincident relation works and no funny stuff like what I was experiencing prior to simplifying was taking place.

If simplified curve and original curve has to be same spline points what is the point of using Simplify Spline tool?

If number of spline points are same in simplified curve and in original curve what is the point of using “Simplify Spline tool”?

I am guessing that there is something going on in the background that the user does not see.

This might be similar to when you place text in a sketch. The sketch remains under-defined unless you use the "Fully Define Sketch" tool. There is no discernible difference between the "before" and "after" sketches, but it is fully defined.

If arc has tangent relation with spline it is coming. But tutorial needs to have coincident relation with spline and arc center.