As for your question about the eldest son and the second son.
First, it is really influenced by Confucianism. If I had dared to waste my children directly, the ministers would never have dared! They dare to force death on this matter! Look at Wanli's decades of struggle for the country. Four stories were dismissed because of the establishment of the prince, and how many will be demoted. I don't know the other sons of Wanli, but Zhu Changluo is a good man. He reversed state affairs and appointed officials within a month. In fact, it developed in a good direction, but unfortunately it died.
Second, there was something wrong with the fertility of the Ming emperors. Without sons, many people have already died. You said that Ming Yingzong, you don't stand Ming Yingzong who? Ming Yingzong's father died in his thirties. Ming Yingzong was the eldest son at that time, only 9 years old. Is it a smaller Zhu Qiyu?
Thirdly, we are not sure whether we can solve the Zhu Yunwen problem, which was later said in the history books. Perhaps he was a more capable politician, but he was overthrown by his uncle who could beat him. However, I also think it is really thoughtless to directly establish the grandson of the emperor.
Fourth, the establishment of the apocalypse, when the apocalypse 162 1 year old, Chongzhen was only 1 1 year old. You can't just 1 1 years old, 1 1 years old and you can't see anything.
Therefore, the succession to the throne in the Ming Dynasty is related to many systems in the Ming Dynasty. For example, the system of enfeoffment of the vassal king, the vassal king will go to the place when he is an adult, and only one crown prince can be left in the capital. Also, in order to prevent the harem consorts from taking power in the Ming Dynasty, many queens in the later period came from the people. So there is basically no problem with my son.