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.
The reported sentence is incorrect. It should say, "She promised you that by the time you got there, she would have finished writing the report." The phrase "would have had finished" is grammatically incorrect and unnecessary in this context.
"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.