Tornadoes occur during severe thunderstorms, typically supercells. So you will typically see thick, often very dark storm clouds. The clouds may take on unusual colors, such as green, yellow, or turquoise. The cloud base itself may appear ragged, and there will usually be a rotating lowering of the cloud base called a wall cloud. The tornado will descend from the wall cloud. See the links for examples of wall clouds.
The tornado is a twister before it hits the ground, it just spins in the sky, kind of
Well, if you fly through sky in the tornado your plane will be crushed.
Nothing happens. The lightning will not affect the tornado.
Damage is done to varying degrees depending on the intensity of the tornado on the Fujita scale.
it stays on the ground until it weakens
Known to storm watchers as 'The cone of silence', where a Tornado retreats into the sky, however, this is not strictly after a tornado, more during, as it usually strikes down soon after.
It doesn't necessarily mean either.
The tornado is not affected. It will continue though the valley as it would over any other terrain.
Air at ground level will then spiral into the tornado and reach great speeds. Any buildings or trees the tornado hits will be damaged or destroyed by the winds.
No particular sky color necessarily indicates tornado activity. It is commonly state that a greenish sky indicates a tornado, but it doesn't need to be gray for a tornado to occur, nor does a green sky necessarily mean there is a tornado, just a severe thunderstorm. In a tornadic storm the clouds may appear green, gray, yellow, or black.
tornado
They either stop play where it lands or redo it