Task Manager, previously known as Windows Task Manager, is a task manager, system monitor, and startup manager included with Microsoft Windows systems.
The new troubleshooting Task Manager is only available in the latest Version 22H2, so do you have that? Check at Settings > System > About. More ...
To restore the default Task Manager of Windows 11, just uninstall the app from Settings > Apps > Installed apps. Find there Classic Task Manager + msconfig ... Download Classic Task... · Windows 7 Task Manager for...
The Task Manager icon is built into taskmgr.exe, so you can't change it directly. However, you can work around this by creating a shortcut with a custom icon.