you can eat all of it
Potato.
The part of the sweet potato plant that you eat is the root. The entire root is edible.
A potato is an edible tuber.
Stem tuber of the potato plant is edible
potato
A parsnip is related to the carrot, native to Eurasia and is not grown in warm climates. The potato is a starchy tuber, is native to Peru and can be grown in warm climates.
Planting potato seeds will sprout potatoes. However, in order to get edible potatoes, you will need to let the potato grow, then once you have a grown potato, you will have to cut off part of the potato and replant it.
Potatoes are a tuber, which grows underground, and are the only edible part of the potato plant.
No, cabbage is not classified as a root vegetable. The edible part grows above the ground. Although cabbage has roots, they are not the edible part. Such things as carrot and potato (where the edible parts grow under the ground) are classified as "root" vegetables.
Oh yes, the potato is edible straight from the ground, although it tastes better if cooked.
A potato produce underground tubers. It is the tubers that are edible.