Ma Xiaojun's memory of Milan is not all false, but their relationship is not as close as he thought before.
I'm not sure everything is true. He said that his memory is very confusing, so I'm not sure that I won't remember it in the future. For example, before they teased Mr. Hu, it should be a manifestation of his memory disorder. The hat won't be blown away by the wind (because the doors and windows are closed and then knocked open by the students who rushed in), but it can't be that the hat was thrown down by naughty students on purpose, because Mr. Hu was facing the hat at that time. It is obviously impossible to put the briquettes into the hat so quickly. So these are contradictions, just rebellions. They did tease the staid Mr. Hu, but it may not be the hat. There is something wrong with his memory.
The attempt to rape Milan should be true. After all, this is a "big event", and the chance of remembering it wrong is very small. Because Ma Xiaojun had been secretly in love with Milan before, he was afraid to say it. Later, it was said that Milan and Liu Yi were still suffering, so Ma Xiaojun was angry and anxious to do it, but it didn't work in the end.
Being stepped into the water by many people in the swimming pool is a symbolic expression. I think it means that Ma Xiaojun, after being gradually isolated by everyone, tried to reintegrate into the collective, but was rejected again and again.
Later, with the growth of age, everyone went their separate ways and had their own lives and careers. Liu Yiku even became a fool because of the war. Those boyhood events are like floating clouds, which are not important to everyone. Naturally, they reconciled. Just like fighting with classmates in elementary school or junior high school. I'm afraid it will be more cordial for you adults to meet. Do you remember that? That's the truth, easy to understand.
The end result is that adult couples are sitting in luxury cars, and everyone is polite to each other when drinking. Compared with childhood, it is very different. Only Liu Yiku, who became stupid because of the war, grabbed the bottle rudely. Then they saw the fool who grew up with them on the road.
In fact, in Ma Xiaojun's mind, a fool, like other buddies, grew up with himself and was a member of his own team, although most of the time this member didn't move with other members. So they are very excited and kind after seeing it. (In fact, fools are abstractions of Ma Xiaojun and others. See the analysis of "The Corner of Fools" for details. You can Baidu it, so I won't go into details here. )
Fools scold them directly when they see them. In fact, what they want to express is the naivety and ignorance of youth and violence, as well as their recognition and alienation from adults.
The above is my personal opinion based on the questions you asked after watching the movie and some film reviews. If there is anything wrong, please correct me and communicate.