Implementation of automatic calculation of Cb

Referencing the image above.

1. Which parameters are required for STAAD to calculate Cb automatically when Cb is set to 0.0?

1.1. For the beam in the image above, which segment is considered by STAAD to determine Cb?

1.2. How does parameters UNL and UNF affect the consideration of segment for Cb calculation?

2. In connect series, how does physical elements affect automatic calculation of Cb?

3. In AISC UNIFIED 2016 the Cb default value is 1.0 against CSA S-16-09/14 which is 0.0, why is AISC manually calculated and CSA automatically calculated?