(2) The quiet stream at night sings the beautiful moonlight under the moon.
(3) Not good. Because "when night falls, everything is silent", even the stream is so quiet that it can only flow "gently", highlighting the silence of the night. If you remove it, it won't have this effect.
④ Write about nightingale, crake, brook, bright moon and nature. As human beings, it gives them human actions and emotions, gives people a cordial and natural feeling, more vividly shows the poetry at night, and makes this poem more infectious.