According to the guys at transair the Zaon unit works with C and S. Not sure if it displays non height related A.
Yes. I use mine on every flight and can confirm that is so.
Once you have one you will be amazed on how many aircraft it "spots" that you dont.
Subject to its limitation regarding non transponding aircraft and given the low cost it is a very worth while safety investment in my mind.
In fact I dont fly without one or full TCAS now.
Moreover the alert function gives you enough time to prevent a collision.