Most of the question 1 is chopped off so I'll try my best to answer.
1ai) In a telephone, the sound is converted into electrical signals before being sent through the wire before converted back into sound.
1aii) Sound travels by the collision between particles. In solids, the particles are closely packed (as compared to air molecules) and thus collide with their neighbors quickly after being disturbed, allowing for sound to be passed on at a faster rate.
b) Can't help much on this one.
