Hi,
1. Zstack will turn on/off radio dynamically according to your application.
2. No, it will pollute the radio channel. Why would you do that?
3. The receivers of ZC and ZR are always on. If you define "RFD_RCVC_ALWAYS_ON=TRUE" in your ZED, it makes your ZED receiver always on.
4. The frequency agility function is also controlled by ZStack.