Most tales are told to illustrate a point of some kind. For instance, the tale of the ant and the grasshopper was told to illustrate the virtues of personal industry. Recently I have seen it altered to illustrate the evils of socialism and greed.
In any event, the tale may be rewritten to delete a particularly horrific portion that does not pertain to the ending of the tale or it might be rewritten to reflect the changing times of the speaker. In order to keep the tale relevant to the audience, it might have minor events or elements edited to keep the tale fresh and new.
A tale from another region might also have elements in it that are peculiar to that region. Such things as peculiar geography, for instance, will not help another region to see the point of the story. For instance, it would do no good to a British citizen to know that Red Riding Hood was going through the Carpathian countryside and X woods was particularly difficult. What they would be interested in was the meeting of the Wolf. The "minor" elements of the tale would be changed to suit the listener.
The original tale of Cinderella was Egyptian and concerned the true story of a female slave who became Queen of Egypt by having her sandal dropped by an eagle at the feet of the Pharaoh. The key elements--shoe, king, lowly maiden--have been changed to reflect the country of the teller, but the story remains the same. This is known as a variant on a tale.
The core theme or central message of the original story tends to remain consistent even as it is reinterpreted by another author. This is because the underlying values or moral lessons that the story conveys are often preserved across different adaptations.
We might call it the message of the story.
What the author might have thought was the theme in the story.
to tell the story in a voice of one of the characters
an author
The Grasshopper and the Ant is generally considered one of Aesop's Fables, written by Aesop, a slave and story-teller who lived in ancient Greece between 620 and 560 BCE. It has been adapted and reinterpreted many times since the 19th century.
Flashback
An example of a short story that I know is the three little pigs. Also, another story that you might know is Pinocchio.
He might want to give the character a name at the end, as a surprise ending.
Because the author of the story decides that way. A different author might have them being the best of friends.
By having the character change in an important way
I think we'll leave that story for another day