Yes, generally erotica adult stories are meant for adults. These stories often contain sexual content that is not suitable for younger audiences. They are designed for those who are old enough to understand and handle such adult - themed material.
Even in more liberal regions, there are still limits and regulations. These stories are not in line with the general social values of promoting a healthy and positive social environment, so they are usually restricted.
No. Such content involving group sex is not appropriate in literature as it goes against moral and ethical values. Literature should promote positive, healthy and respectful relationships.
Group sex real stories often involve situations that are not ethical in most moral and social frameworks. In many cultures and religions, sex is considered a private and monogamous act. Group sex goes against the principles of fidelity, respect for others, and the dignity of the individual.
No. Writing such stories is often not appropriate as they involve sexual content which is not suitable for general public consumption and goes against moral and ethical norms in most contexts.
The ethics of these stories are debatable. Some might argue that as long as they are clearly marked as erotica and are for consenting adult audiences, they are okay. But others may think that they objectify characters and promote a narrow view of sex.
Yes, they are likely only for adults. Given the nature of the content which is likely to involve sexual themes, it's not appropriate for minors. Society has norms and laws in place to protect the innocence of the young from such adult - oriented materials.