The system you bought is wireless equipment.
Wireless means the camera can connect NVR by wireless method, but it doesn't mean NVR can connect router wirelessly. Please don't misunderstand it.
1. Why is there an ethernet cable in the package?
The ethernet cable in package is used to connect NVR to the router to get Internet, not used to connect the camera to router.
2. Why is there an ethernet port at the end of the camera and 4 ethernet ports at the back of NVR?