1. How to name a Oneshot or Bonus Chapter of a manga?
Oneshot and bonus chapter are not the same thing. People do not rename chapters as Oneshot, but rather mark them as such by ticking the
"This is a Oneshot" box. When checked, the chapter and volume columns become disabled and grayed out
As for Bonus Chapter, you can upload it just like any other chapter, but because it is not a regular chapter, you may need to specify some detail. For example, if given chapter is a bonus volume chapter, you may use x.5 as chapter number regarding the case
2. How to mark "END" in the last chapter of a manga?
Fill in the final chapter column if you have access to title editing. When you post a chapter with the same chapter number as the final chapter, it will be marked automatically as END. However, if you do not have access to title editing, you can report that chapter as END chapter, explain why, and then wait for MOD to evaluate and alter it for you
For more information, read similar thread:
How to Mark Chapters with END
