Yes, if the seed is viable.
Potting soil does not grow. It is not a plant, but a medium in which to grow plants.
This depends on the species of plant. Some plants require different nutrients than others. Your best bet would be to plant in regular soil, and then after some research you can till the soil with the required nutrients.
Marijuana is not in any plant - it is a plant. Cannibus Sativa is the 'Marijuana Plant'.
Some plants grow better in certain types of potting soil
Potting soil does not grow. It is not a plant, but a medium in which to grow plants.
You have baby marijuana plants
"Plants" is too broad a term. Try naming a certain species of plant to get a better answer.
No, marijuana plants are a soft bush. Perhaps you are thinking of hemp (Cannibis Sativa), which is a plant of the same family as marijuana.
Most plants will grow better in potting soil because it contains nutrients the plants need to grow and is formulated so the water will drain slowly enough for the roots to take up the water, but not so slowly to cause the plant to rot. Roots can grow freely and anchor the plant easily.
Marijuana comes from 2main types of plants the sativa which is a tall plant with skinny leafs and the indica plant which is short with thick leafs.
The plant is probably dying
Leaves, like any other plant