The french horn usually plays the same part as the violas. it is used for creating background sound in the orchestra.
French horns do have valves, but not the same kind trumpets use. Trumpets use pistons, and french horns use Rotary Valves. However, a marching french horn, a melophone, does have piston valves.
yes there are.
You say "horns" in French as "cornes."
French Horns are good because they teach you music and play ALL kinds of notes.
yes
Yes
addaxs horns
yes cows do use their horns for fighting
See below
French horns, mellophones
Modern horns evolved out of old style hunting horns.
It evolved out of hunting horns in Germany.