Hi 1 is correct because of the punctuation.
Yes.
No, The correct grammar for this sentence would be, "He finished doing his homework."
their
No, the sentence is incorrect. Correct: After the professor finished, the class was very confused.
Yes it's correct.For example, "would you mind if I finished this later?"Finished is the past tense of finish.
"How are you" is a correct sentence.
A and
Well, it's almost correct. But since it asks a question, it should end in a question mark (?). I would also call it an interrogative sentence rather than a demonstrative sentence.
Yes, this sentence is correct.
You are palpitating. This is a correct sentence.
With the exception of not capitalizing the 'y' at the start of the sentence, it is a correct sentence.
A correct revision would be: I worked hard all day so I could go out that night; I almost finished the entire project!