Federal law says an unlicensed individual may transfer to or receive from an individual who resides in the same state with no FFL or 4473. I can move to the same state my daughter lives in, and bring my guns, and then give her one, but if we are not both legal residents of the same state, I must transfer to an FFL in her state and she must do the 4473.
There are some differences in inheritance procedures, but, since you and your Dad were both CA residents, those don't come into play UNLESS you move to North Dakota before taking possession of them from the estate. If that happens, you may be able to do it without FFL aid. Be sure of N Dakota's laws and if there're any registration requirements there. They've sure gummed up the works, haven't they!!!
(Question 2)
https://www.atf.gov/resource-center/docs/0501-firearms-top-10-qaspdf/download
So, as an unlicensed individual, you can only receive your Dad's guns from the executor in a state where you are a legal resident, which is also strictly defined in Federal law, and the inheritance exceptions don't change that requirement. If the executor moves the guns to another state to escape CA's clutches and paperwork, you both must either be residents of that state before you receive them, qualify for the exception above, or go through an FFL in your state of residence at time of transfer.
If I were the executor, I'd check quietly into CA's laws and see if he is required to, as the legal owner, comply with any CA laws prior to moving them out of state. CA law is what happened when NY law and NJ law had a baby. I will NEVER set foot in CA.