view range and snap problem

[Cheuk Ling]

Hi all,
Inside this file , I have drawn a sloped wall.
Two questions :
1. I set the view range to be zero, both top and bottom plane
are at level 2. But I can still see through the wall (from cut plane to bottom)
why ? What can I do if I just want to see the cut face only ?
2. I can only snap to the bottom of wall , but cannot snap the cut face.
What tricks can I apply to make it snappable ?

thanks for all response.