Could you please tell me if the questions are grammatically correct? Thank you very much.

1) What does the word “rub” denote and connote?
Why does Hamlet arrange a play at court? What is the function of the “play within the play”?
2)Whose ghost appears to Hamlet? Why? How does the play end?
3) What did the Latin statement “quietus est” refer to? Why does Hamlet refer to it (I need a synonym of "refer"?
4) How does Hamlet regard courage and cowardice respectively?
Can Shakespeare’s Hamlet be regarded as a revenge tragedy? Why? What are the main features of a revenge tragedy?
5) From which perspectives does Hamlet consider death in his famous soliloquy “To Be or not to Be”?

All are fine.

http://thesaurus.com/browse/refer
I'd stick with "refer," but it you must replace it, then use either "allude to it" or "point it out."

1) To check if these questions are grammatically correct, we can analyze each of them separately:

a) "What does the word 'rub' denote and connote?" - This question is grammatically correct. It is asking about the meanings and implications (denotations and connotations) of the word "rub."

b) "Why does Hamlet arrange a play at court? What is the function of the 'play within the play'?" - These questions are also grammatically correct. The first question asks for the reason behind Hamlet arranging a play at court, and the second question seeks to understand the purpose or role of the "play within the play."

2) Let's analyze the questions within this set:

a) "Whose ghost appears to Hamlet?" - This question is grammatically correct. It asks about the identity of the ghost that appears to Hamlet.

b) "Why does the play end?" - This question is grammatically incorrect. It should be rephrased to clarify and specify what play is being referred to.

3) The question in this set is as follows:

a) "What did the Latin statement 'quietus est' refer to? Why does Hamlet refer to it?" - The first part of the question is grammatically correct. It asks about the meaning or reference of the Latin statement "quietus est." The second part of the question, however, should use a synonym or rephrase "refer to," such as "allude to" or "mention."

4) Now let's analyze this set of questions:

a) "How does Hamlet regard courage and cowardice respectively?" - This question is grammatically correct. It asks about Hamlet's views or opinions on courage and cowardice.

b) "Can Shakespeare's Hamlet be regarded as a revenge tragedy? Why? What are the main features of a revenge tragedy?" - These questions are grammatically correct. The first question asks if Shakespeare's play "Hamlet" can be considered a revenge tragedy, while the second question seeks an explanation by asking for the main features or characteristics of a revenge tragedy.

5) Finally, let's analyze the last question:

a) "From which perspectives does Hamlet consider death in his famous soliloquy 'To Be or not to Be'?" - This question is grammatically correct. It asks about the different viewpoints or angles from which Hamlet contemplates death in the famous soliloquy "To be or not to be."

Overall, the majority of the questions are grammatically correct, with a couple of minor errors that can be easily rephrased for clarity.