What is the difference between the following sentences?
My father will have reached home by now. You are absolutely certain that your father is at home, that he has arrived by now.
My father should have reached home by now. Enough time has passed that you believe that your father is probably home by now (you may have previous experience of how long it takes him to get home).
My father must have reached home by now.
It has now been quite a long time since he left to go home, so you think that it's not possible that he could still be travelling. You would be extremely surprised if he weren't home by now.
Thanks very much in advance.
See above. As you can see, they're all correct but mean different things.