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Observation:
When light is shined on the radiometer, the vanes (flags) start to move. The black vanes move backwards and the white/silver vanes move forwards.
Explanation:
The shiny white surface of the vane is a better reflector of radiation. In a good vacuum environment, the vanes move due to a force from the radiation.

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Observation:
Fastest—Slowest:
Copper, Aluminium, Steel, Glass, Plastic,Wood
Explanation:
Since the rate of conduction of thermal energy in descending order is copper, aluminium, steel, glass, plastic and wood, the thermal energy is conducted from the hot water to the paper by the rods in the same order. Thus, the paper for copper dries the fastest, following in the same order, thus the color change rate.

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Observation:
They rotate in the direction the silver vanes are facing.
Explanation:
When the vanes are exposed to light or infrared radiation, the black vanes absorb more thermal energy than the silver vanes, hence air particles on the black side move further apart than those on the silver side, increasing air pressure. The difference in air pressure on the two different coloured sides results in an air current (wind) turning the vanes.

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If there is an insulating material in the middle of the circuit, how is it that the circuit can be closed?

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I believe the actual connecting wire is hidden from view (see red dotted part). The insulating material is likely there to prevent direct heating of the bimetallic strip by the light bulb via radiation.