Hello,
         I will try to answer your questions as best I can, it's good to
     see
     young people learning about a really interesting insect.
     1) Drones don't leave the hive to collect nectar, they are fed by the
     "house" bees inside the hive, older drones may feed themselves
     directly from
     honey cells, once the drones become older.
     2)Drone frequently drift into neighboring hives, the guard bees seem
     to
     pretty much ignore the "strange" drones, indeed this is one way in
     which
     disease can be spread from hive to hive, worker bees are a different
     and the
     acceptance of a drifting worker will vary from hive to hive,  during a
     good
     nectar flow a drifting worker is more readily accepted into a strange
     hive,
     during a nectar dearth the strange bee is likely to be turned away (
     by
     various means) or even stung.
     3) Bees actually "learn" to pollinate alfalfa, they must "trip" the
     flower,
     which can actually hit the bee quite hard, experienced bees can be
     observed
     avoiding being hit by the structure, some say this is evidence of
     learning
     conditioned response).