When using RSU, is it necessary to use an external trigger to trigger the FPGA to load the application image?

I got some problems when using RSU in Cycone IV E device:

1: When using RSU, is it necessary to use an external trigger to trigger the FPGA to load the application image?

2: Why can't I get the reason for reconfiguration by reading the register when the application image fails to load and returns to the factory image?

3: The same loading process, why use the avalon-mm interface in the factory image I can not trigger the FPGA to load the application image, but the non-avalon-mm interface can trigger?