I have no idea what your question is.
You can earn a sniper skill point by killing four zombies, with a sniper, in a row, you need 300 skill points to execute a headshot inside pvp.
It's simple, Because the skill doesn't say rifles skill, it says sniper rifle skill & that hunting rifle is not a sniper rifle.
Because you cannot even skill the weapon even in the original game. No matter how many kills u make the stand be same, the walk be same the accuracy will be same the fire rate will be same in other word every thing is the same from skill 0-1000.
No you cannot. There are only 3 weapons you can perform headshot, in pvp, in this server Sniper, combat shotgun, deagle.