Definitely. The duration of a story is only restricted by your imagination and the requirements of the narrative. You can go way beyond 15 seconds to build a rich and compelling tale.
In some cases, you can repost a longer story if the copyright allows and the platform supports it. However, you need to be cautious about violating any terms of use.
Yes, it's possible. You could expand on the characters' backgrounds, add more events and complications, or elaborate on the setting and atmosphere to make the story longer than 15 seconds.
It depends. Making a story longer than 24 hours requires a rich and engaging storyline, well-developed characters, and a coherent narrative structure. Without these elements, it might just become a drawn-out and uninteresting tale.