@v4 I think there´s already a plugin that lets you do that, show the N last posts from a category in the home page. Since you only have one category, i think that meets your requirement. Check the plugins category in this forum, i think you'll find it there.
shall admin prevent users to add new tags in nodebb?
I'm a novice develpoer, and I DO NOT WANT MY USERS TO ADD NEW TAGS. How can I do for it. Or can I delete some tags?
Search "tags" in the ACP search bar. There should be an option to manage tags and only allow certain ones.
@PitaJ is correct, the option is called the "tags whitelist", and you can decide which tags to allow, and do so on a per-category basis