On question 1, the saying "What goes up must come down" is appropriate. If you fire a gun into the air on New Year's Eve, the bullet will travel up to a mile high (depending on the angle of the shot and the power of the gun). Once it reaches its apogee, the bullet will fall. Air resistance limits its speed, but bullets are designed to be fairly aerodynamic so the speed is quite lethal if the bullet happens to hit someone. In rural areas the chance of hitting someone is remote because the number of people is low. In crowded cities, however, the probabilities rise dramatically and people get killed quite often by stray bullets. Most major cities have laws in place to try to keep people from shooting guns into the air in celebration. Here are two news reports on the subject:
Question 2 is one of those funny questions -- like "which weighs more, a pound of lead or a pound of feathers?" -- that seems surprising the first time you hear the answer but then is obvious afterwards. The bullets hit the ground at the same time provided that the gun and the ground are level. The reason they hit the ground at the same time is because gravity doesn't care that the bullet fired from the gun has horizontal velocity. Gravity acts vertically. Gravity accelerates both bullets vertically at exactly the same rate, so they both hit the ground at exactly the same time.