DRA821U: Power isolation to ASIL-D

Hi

I'd like to know about power IC solution with DRA821U which can support ASIL-D.

I'm referring Figure3-2 in https://www.ti.com/lit/ug/slvuby7/slvuby7.pdf

Q1) If we don't separate power supplies by domain, will we not be able to achieve ASIL-D?

Q2) Want to learn more about domain power isolation.

                  Isolation by Load SW

                  isolation of power generation devices

                 etc....

Q3) We will use only MCU domain.
       If domain power isolation is required for ASIL-D, is it possible to have a configuration where only the MCU domain is power supplied and (not all but) only required part of main domain is power supplied, and separate these power by Load SW?

      Or, Do I have to power the entire main domain? (And we cannot separate it by Load SW?)

Thanks and Best regards,

Tsurumoto.