"you alone are cursed." The word "curse" is first in Hebrew in order to emphasize the contrast between God's blessing on the animals and this curse on the serpent. This is a "curse formula," or the way that curses were expressed. By saying this curse, God made it happen.
"You will move along the ground on your stomach." The words "it is upon your stomach" comes first to emphasize the contrast between the way other animals would move along using their legs and the way the serpent would slither along on its stomach. This is also part of the curse formula.
"you will eat dust." The words "it is dust" comes first to emphasize the contrast between the plants above the ground that other animals would eat and the dirty food on the ground that the serpent would eat. This is part of the curse formula.