There are several common themes. Morality is a big one. For instance, in 'Pinocchio', the story teaches about lying and the importance of being honest. Another theme is discovery. In 'Where the Wild Things Are', the boy discovers a whole new world. And then there's the theme of perseverance. In 'The Tortoise and the Hare', the tortoise shows that slow and steady wins the race, which is all about persevering.
I'm not sure specifically as I don't know which 'the contest short story' you are referring to. It could be about a competition, perhaps a writing contest where the story itself is either the entry or about the experiences within the contest.
A very lovely children's short story is 'The Ugly Duckling'. It's about a little duckling that is different from the others and is often made fun of because it looks 'ugly'. But as it grows up, it turns out to be a beautiful swan. This story tells children that everyone is special in their own way and not to judge by appearances.
Well, for a YA short story contest, common requirements include a word count range, like 3,000 to 8,000 words. Also, the story might need to fit within a given genre or topic. And often, there are rules about originality and submission format.
First, have a clear understanding of the contest theme. Then, do extensive research if needed. Polish your writing, check for grammar errors, and make the story emotionally resonant with readers.
I'm not sure specifically as there could be many stories titled 'the childrens story'. It might be about the adventures of children, their daily lives, or some moral lessons for kids.