Yes - Turtles are "born" with a shell. In the first days after hatching the shell can be softer, because their bones are not calcified all the way yet. Once fully grown, turtles and tortoises have...
i think it would grow with the turtle and then when it is an adult the shell would be fully grown
turtles do not shed their shells.
no because it needs time to form
yes only if it's bits and pieces. if it's a large crack and bleeds, then eventually the turtle will die.