1. We should arrive before dark.

Question

2. I should have finished the book by Friday.
[In the Oxford dictionary, I saw the two sentences. They mean 'guessing.'
What is the similar expression for #3 in American English? Would you check the following?]
3. I would have finished the book by Friday.
4. I will have finished the book by friday.

Answer 1

1. OK

2. This sentence means "I ought to have finished ... , but I didn't."

3. This sentence is making an excuse to explain why he/she didn't finish the book by Friday.

4. This sentence is stating that he/she will be finished reading the book by Friday.