Hello there,
I typed cullcontrolpolygon to make it off but sub d object’s vertex can be selected.
when it is off: Ok
**
when it is on: Won’t work. It selects back vertexes too.
It works only if I hit F10 and open control points.
In 3ds max, there is “Backface” for culling and it works.
Last thing,
Could you copy cullcontrolpolygon icon to Subd Edit toolbar please? I know I can add myself but if you could, it would help many people.
Has anyone ever experienced that before or the problem exist in your side too 
It seems like this is the intended behavior of CullControlPolygon. From the help:
The CullControlPolygon command hides surface points, mesh points and SubD points (turned on by the PointsOn command)
Some commands can help select visible vertices only: Lasso SelectThroughObjects=No, or SelBrush SelectThroughObjects=No for example; all with a selection filter active for vertices, “Select sub-objects” active, and in a shaded mode.
See this work ticket too: RH-62607 Selection Filters could use a ‘select through’ checkbox
I will try lasso selection thank you a lot. Fence selection can be added too, it is a New and nice tool for trim command in v9 
that can be adopted maybe
Do you mean the SelFence command? (Rhino BETA Feature: Fence Selection and Selection commands | Rhino 3-D modeling). The Beta version has a new SelectThroughObjects option.
Or you can use SelBrush (Selection commands | Rhino 3-D modeling) which does the same thing, and is already available in v8, except that it uses a “thick” brush path instead of a thin polyline for intersection.
