Some things remained unclear

Just watched it yesterday with GF, the ending was confusing for me too.
1. It's boys meeting after many years, you can see all of them are much odler and for me even impossible to recognize their characters.
2. Dunno.
3. He wanted to have sex finally.
4. I guess, although students were chasing teachers, that would make it more rel, but you could see lack of respect for teacher because he was educated and that was not welcomed.
5. At that time and in general Chinese are quite conservative, boys hanging with boys, you could even see resisting kiss from girl instead enjoying it, so having boner was quite shameful, although it's perfectly normal and accepted in normally raised culture.

Peter Markoff
The best - Fight Club, American Beauty & Falling Down.

I watched this film this summer and I really like it.
Here are some of my personal opinions about this film.
1.the Chinese name of this film is "the days when the sun shines bright"(my own translation:-)
And you can see the story happened mostly on sunny days.
In the end,it turned black and white because the sunny days were over.And the boys grew up.And they would never do or dream stupid things any more.Some actors were changed so the characters looked older(that's why you can't recognize some of them:-)
2.This film was adapted from a short novel called "Wild Beasts"I've never read it.But I recommend it to you.You can learn more about that time and the main characters from the book.
3.I think he just wants to have sex with her so that she will be sth. more real than a fantasy.
4.The teachers were the first ones to get prosecuted because knowledge was considered useless and dangerous at that time.Students paid no respect to their teachers and beat their teachers,put them in prisons.It was a mad time.
5. I think there are two reasons.First because the gang leader thinks the girl belongs to him,he won't allow others to think sexually about that girl.Second maybe it's quite a shame to behave like that in a public shower room.China is a very conservative country after all:-)
I'm a native Chinese speaker,and it's my first time to comment.
So feel free to ask me if you don't understand my reply:-)

1. The five dudes reunite as adults in the present day (1994), with some changes in their statuses and group dynamic. Some appear more successful, others seem a little more submissive. Their gang leader and previously ladies' heartthrob Liu Yiku apparently went mad due to his war experience in Vietnam and now acts like a mental case. They encounter the mentally challenged kid from their compound, still riding that wooden stick. They call out the childhood catchphrase "gooloomoo" and expect him to reply with the usual"ouba", but he just yells back, not without some irony, "retards!", clearly no longer remembering the catchphrase or the gang.

2. I think your guess is as good as anyone's. I don't think it was the intention of the writer to make it clear what dark secret she has, only that she isn't the perfect spotless angel pubescent boys imagine their crush to be.

However, when Monkey joked Mi Lan looked like she's just had a baby, it was really just him trying to cope with the fact she wasn't interested in him romantically. Of course at this point both Mi Lan and her love interest Liu Yiku assumed these insults from Monkey were only friendly banters.

Still, that doesn't rule that out. Probably she did get pregnant and had an abortion. At one point she mentioned she was ill for some time and did act all secretive and private and Monkey asked her what her illness was.

3. He attacks Mi Lan and acts like he was going to rape her. But after she sits on top of him and beats him up, it was vaguely implied that she actually initiates a move by unbuckling his belt, which is when he resists and moves away from her with pants down at his ankles.

I think Monkey was attacking her mostly out of spite and not out of sexual desire. He was frustrated that Mi Lan wasn't into him and his defense mechanism (noticing her imperfections like her plumpness and realizing her ambiguous history with disreputable characters) failed to completely turn him off her. But when she actually proceeds to take his pants off, he was immediately repulsed.

Does that mean he would've gone through with it if Mi Lan did nothing? I think that question is open-ended.

4. No, just kids being out of control. To put it mildly, intellectuals weren't taken very seriously during the Cultural Revolution. According to the narrator, that high school was one of the few that still had some resemblance of order.

5. Liu Yiku was more or less in a friends-with-benefits relationship with that girl Yu Beipei. Sure she acted like one of the guys, but that doesn't mean the other guy had any right getting aroused by her wet-T-shirting. Haha.