You lecture me about "history," yet your own historical knowledge is a complete joke. Let's look at the actual timeline:
1. Before your country even existed as a state: As early as the Han Dynasty (2nd century BC), Chinese people had already discovered, named, and lived on the South China Sea islands. During this entire period, the northern part of what you now call Vietnam was literally a province/county directly governed by Chinese dynasties. How can a state claim "ancient sovereignty" over islands where Chinese people were already living before that state even came into existence?
2. The "Vietnam" name itself: The name "Vietnam" (Việt Nam) didn't even exist until 1804, when it was officially granted by Emperor Jiaqing of China's Qing Dynasty.
3. Your official betrayal in modern history: In 1958, North Vietnamese Prime Minister Pham Van Dong sent an official diplomatic note to China explicitly recognizing China's sovereignty over the Paracel (Xisha) and Spratly (Nansha) Islands. Official Vietnamese geography textbooks up until 1974 clearly marked them as Chinese territory. You only flip-flopped and backstabbed after receiving tens of billions in Chinese aid and unifying your country.
From taking massive historical aid and then tearing up official diplomatic promises, to this game creator accepting free localization from Chinese volunteers and then turning around to provoke players—backstabbing after getting what you want seems to be a habit for you. Learn your own white-and-black history before trying to lecture others.