Man is a conductor, equivalent to an antenna in space. He can induce electromagnetic fields around him, such as wires, and form induced voltage on human body. After touching the touch switch, this voltage is input to the amplification circuit in the touch switch, and after amplification and shaping, it forms a trigger signal to turn over the internal bistable circuit, and then triggers the thyristor to turn on the circuit and make the lamp shine.

Can only answer your first question.