CN0407 system calibration

Hi,

We're designing ADA4530-1 in our new product. We use CN0407 as our reference design. We have some questiones about the schemetic. Could you help us?

1. Does RC circuitry (RN1 (1-8, 2-7) and C47) work as a passive RC filter? Will it be better if we add an op amplifier, i.e. an active RC filter?

2. Why do you add RN1 (3-6, 4-5) and C9 to the input of AIN1? What do you concern about?

3. If we want to do system zero-scale and full-scale calibration, which channel should be active? Do you have reference code for system calibration?

Thanks in advance.