Here a user TRomano gave me advice to ask this question that I don't understand.
I can come back later, off to work now. But why not ask a separate question about "shall have had to" and "should have had to" and I'm sure others will answer.
What do "Shall have had to" and "Should have had to" mean?
- We should have had to work diligently.
- We shall have had to work diligently.