Hello,
Concerning your first inquiry, please refer to the Ansys help excerpt: "Note that you can only display smooth contours if node-values are enabled." (To enable it, use the command "display/set/contours/node-values?")
As for your second question, I'm not entirely certain, but one possibility is to exclude those boundaries when selecting the surface using the command "display/set/contours/surfaces."
Thanks,
Nikhil