Is it possible to force the clouds to produce hail?
Hail is hard... you need updrafts strong enough to keep the stones in the air, and freezing temperatures with 100% humidity. Unless conditions were perfect for a thunderstorm in the first place, you'd need huge amounts of energy.Humans do not use energy on that scale yet.
Not unless you're God or Mother Nature!
Not yet, but scientists are working on how to "seed" clouds to make it rain places that need it.