No, it is not necessary to have an internet connection to use the Wi-Fi feature of the trail camera. The Wi-Fi feature allows you to connect your smartphone directly to the camera's network. 

A Wi-Fi trail camera utilizes a wireless local area network (WLAN) to send images and videos to a smartphone, tablet, or computer for remote viewing. This type of camera does not require a cellular service plan, as it can connect to a router or access point within range. On the other hand, a cellular trail camera uses a cellular service plan to send images and videos to a smartphone, tablet, or computer. It is able to embed GPS coordinates within the image, making it easier to locate the camera. Furthermore, cellular trail cameras are able to send images and videos to a remote location with no need to physically retrieve the device. This feature requires a cellular service plan with data, which can be costly. Overall, a Wi-Fi trail camera is best suited for connecting to a local router or access point, while a cellular trail camera is best for sending images and videos to a remote location. 

Yes, you can control the trail camera using your smartphone through Wi-Fi. You can change the camera settings, view the live feed, and download the photos and videos captured by the camera. 

The Wi-Fi signal of the trail camera can reach up to 100 feet in an open area. However, the signal strength may vary depending on the obstacles and interference in the area. 

It does not need an existing WIFI network. The Unit itself generates its own "hotspot" to connect to your phone wirelessly - functions similar to connecting via bluetooth, but uses WIFI instead to be able to download photos faster.