In kit building when to use CA and when to use epoy?
 

in a word... overkill.

Every glue mentioned will form a bond signifigantly stronger than the surrounding wood if used correctly and not subjected to its own environmental soft spots. In normal flying use, the real discriminators are convenience and health effects, and then you've got cost, weight, and appearence for tie breakers.

Talking about glue is like talking about God -- we each use it our own favorite form chosen from a whole bunch of forms. And every one of us either knows his form is the only right one, or else he just doesn't know. Experiment a little and use whichever you like among the recommended types -- you'll be fine, I promise.

In kit building when to use CA and when to use epoy?
 

Yea I used CA for gluing the balsa and epoxy to join my foam wing halves.This is kinda off topic,but when I broke my ankle and had surgery when they took the staples out they put CA on the incision.Kinda weird,there is also a commercial on tv about a new product to close wounds without stitches and the main ingredient is CA.