Link is left handed in all Zelda games thus far, except for the Wii version of Twilight Princess. He holds his sword in his left hand in this game, except when he is facing East.
After getting the magical powder, head straight to Kakariko Village. Once there, find the old woman who is outside sweeping and throw the powder on her and she will turn into a fairy. While still at Kakariko Village, go inside the house directly to the left of the merchant and lift up the first pot to reveal a chicken. Throw the powder on the chicken and it will turn into a human.