The Call of Duty series games are made in IW engine by Infinity Ward. You probably would've seen the name when you start any COD series game. Almost every game shows the game engine which it is built in. The IW game engine uses c++.
Players who receive voice chat warnings or in-game voice communication penalties can still play the game. However, per the Offensive Behavior section of the Call of Duty Security and Enforcement Policy, extreme or repeated offenses may lead to a permanent suspension from playing the game online.
Call of Duty: Black Ops IV is a payed game, which you need to purchase as a disc (physically) for your Xbox One/One S/Series X or digitally on the Microsoft Store, for any Xbox One/Series X|S console. Because of that, this game requires an active Xbox Live Gold subscription or Xbox Game Pass Ultimate.
Fans are disappointed as the Game Pass didn't include a single Call of Duty game. Phil Spencer, CEO of Microsoft Gaming, confirmed last year that Activision Blizzard video games will hit the Game Pass in 2024.
If you can't find Vanguard or Battlenet within Windows Defender Firewall's allowed app settings, click the Allow another app button. Then click Browse to select Vanguard or Battle, and press the Open and Add buttons. After adding those apps, you can configure their firewall settings as outlined above.