Often, online bookstores or reading platforms offer previews. Just look for a 'Preview' or 'Sample' button. Also, some authors share snippets on their blogs or newsletters.
It depends on the platform. For example, on a social media platform like Instagram, there might be a specific button or option to preview your story. To schedule it, you may need to access the settings related to your story creation. Usually, there are menus that allow you to choose the time and date for the story to be published.
Maybe look for reviews or comments about the story. People's opinions can give you a sense of what it's about without opening it yourself. Also, sometimes there are teasers or trailers available that offer a glimpse.
I don't have the specific date for when the Egghead Arc started in manga off the top of my head. But you can probably find it by researching on manga-related blogs or by asking fellow manga enthusiasts.