DFT and Scan Circuits

[promach]

1. For set_autofix_configuration -method , when should we use gate ? and when should we use mux ?
2. May I know why the only way to guarantee no scan hold time violations is to use LSSD ?
3. How is the proposed circuit in Figure 3 being low power, and hold friendly ?
4. How is adding an inverter to pin D avoids performance degradation introduced by the MUX ?
5. How to derive the general formula of the scan test length ?
6. Once converted to scan sequences with a 6 vector Shift test, 44 vectors result ?