Depends on how many you have to begin with, it's much easier for guys since we have deeper voices already and can extend to the falsetto. Female singers can but they would have to go up to the whistle register to do so since the really can't go as low.
Yes as long as you already have a good range, whistle notes can be done by anyone as long as you learn it correctly. Beyonce has already shown 4 octaves of singing voice f2-f6 and I'm sure she already knows the whistle technique but would rather not use it since its quite damaging.
