Well, VF condition in comics implies that the comic book has some minor flaws or signs of handling but is still in a good state. It might have slight creases or very minor spine stress, but overall it's considered a high-quality collectible.
To keep a secret, I first try to forget about it myself. I don't let it linger in my mind too much so that I'm not tempted to share it. Also, I avoid situations where the secret might accidentally slip out, like when I'm drunk or really angry.
Perhaps the secret is that Lucy has a unique magical item that is very powerful and dangerous. Natsu keeps it a secret because he doesn't want other mages in Fairy Tail to get greedy or misuse it. This item could be something that was passed down in Lucy's family and she doesn't fully understand its potential yet.
Honestly, 'VF' in comics can have multiple meanings. It could be a code or nickname for a certain comic element. Sometimes, it might be an initialism for a fictional organization or a power or ability. You really need to look at the specific comic and its surrounding details to figure it out for sure.
It really varies. Some manga have characters who can keep secrets well, while in others, secrets are spilled easily. It all depends on the story's context and the personalities of the characters.
It really varies. A well-crafted secret in a novel can make it more intriguing. But if not handled properly, it might seem forced or predictable. The key is how the author reveals and plays with the secret throughout the story.
The key is to build suspense. Don't reveal too much too soon. Make readers constantly wonder and guess. And have characters who are cautious and paranoid about the secret being discovered.