There is an answer and it’s the one I already gave. There are always edge cases and exceptions because there are an absurd number of variations and vehicles types. By and large I already gave the deciding definition, and it is in what I linked as well as many others places.

Edmunds - “Traditional 4WD systems have a two-speed transfer case with high- and low-range modes that can be selected by the driver, either with an electronic switch or a mechanical lever.”

CARMAX - “Key to how a 4x4 works is a piece of equipment called a transfer case. This connects the vehicle's front and rear wheels, splitting the engine’s power evenly between them and making both axles turn at the same speed.”

And the article didn’t list the rules because it was wrong about everything. The rules are listed by the National Park Sevice. “A four wheel drive vehicle is defined as a sport utility vehicle (SUV) or truck with at least 15-inch tire rims and at least eight inches of clearance from the lowest point of the frame, body, suspension, or differential to the ground. Four wheel drive vehicles have a transfer case between the front and rear axles that locks the front and rear drive shafts together when four wheel drive is engaged. All wheel drive (AWD) vehicles do not meet this definition.”

So again, repeating yourself doesn’t make you more right. It does however increasingly make you look like an ignorant ass that has no desire to actually learn anything.