Season 4 of Haikyuu begins approximately at chapter 290. But keep in mind that there might be some variations depending on different translations or editions.
The ending of season 4 of Haikyuu in the manga is at a point where a major plot development occurs. It's a bit complex to pinpoint exactly, but it's related to a key match or event in the story.
It ends at a specific chapter that focuses on a crucial match and character development. But I can't recall the exact chapter number off the top of my head.
The start of Haikyuu Season 4 in the manga is approximately at chapter 290. This might not be exact as sometimes there are differences in how the content is presented and divided between the two mediums.
They might be really surprised. Some characters could be amused by the creative scenarios fans come up with. For example, Hinata might be excited to see himself in all kinds of wild adventures in the fanfictions.