yes or if one knee touches the ground
No, unless his knee also touches the ground at the same time.
yes if his hand touches the ground he is down but only if he is touched by contact and then touches the groundNo. A player is down only when a part of his body other than a hand or a foot touches the ground, or when the officials rule that his forward progress has been stopped.
No. They are down when any other part of the body hits the ground besides a players' hands or feet.
No ... if the shoulder, elbow, forearm, or wrist touch the ground the ball carrier is also considered down.
The ball carrier is not down if his hand touches the ground. He is however ruled down if his elbow or knee touch during a run.
A tornado that touches the ground is simply a tornado. Before it touches down it is called a funnel cloud.
A person levitating
If the football itself touchs the ground while you have possesion then you are not down.
Each football league will have its own rules and regulations which may differ compared to other leagues.In other words, it depends on which league one is asking about.