1. They ended/finished the celebration at 3 A.M.

Here either ended or finished is correct, isn't it?

2. The celebration ended at 3 A.M.

It is said that the sentence 2 is grammatically correct.

3. The celebration finished at 3 A.M.

It is said that the sentence 3 is ungrammatical because of the verb 'finished.'

I have brought these example sentences from my book with explanatioin, but I just don't see the difference between the 2 and 3 even though 3 is said to be wrong because of some reasons according to my book. (and the sentence 1 is correct but 3 is wrong which makes me very difficultEmotion: surprise)

Do you not say 3? and can you say it is grammatically wrong?

They are all OK.

#3 is fine. All your sentences are fine. Your book is terribly wrong. Cast it into the abyss.
Students: Are you brave enough to let our tutors analyse your pronunciation?
Thank you for that encouragementEmotion: smile.

Actually, I don't know if they are from the book(it can be).

I brought them from a mock test question sheet.

The question is:

Explain the reason for the grammticality of (5b) and the ungrammticality of (5c), focusing on the relation the volition of the agent and the ending point.

(5a) They ended/finished the celebration at 3 A.M.

(5b) The celebration ended at 3 A.M.

(5c) The celebration finished at 3 A.M

To me, the question makes me irritated because it looks that it asks rubbishEmotion: indifferent

What is your opinion of the question and the answer?
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All I can see is that 'finished' suggests a completion, while 'ended' merely suggestions a termination.
Ah,, I have clearly understood it. Thanks a lot.

(finish- completion, end- merely termination^^)

The answer given by the questioner stated with the relation to the volitionEmotion: indifferent

As you agreed that the question is rubbish, I don't think I need to copy it and show you.