Sakura doesn't use battle axes in the manga. The manga depicts her with a set of abilities and tools that are distinct from battle axes. It's possible you might have gotten some misinformation or have a wrong impression.
Sakura remains alive throughout the manga. The story doesn't have her character meet such a fate. Her role and presence continue until the end without her dying.
[Battle Through the Heavens Sakura manga can be viewed online.]
I don't really know. It's possible that the creators haven't made a decision yet or there might be some behind-the-scenes issues affecting its continuation. You might want to keep an eye on official manga announcements.
No, Killua doesn't use fire in the manga. His abilities are focused on other aspects like speed and electricity manipulation.
Yes, Goku does use Kaioken in the manga. It's one of his signature techniques to boost his power.
Yes, manga often uses hiragana. It's one of the writing systems commonly employed in Japanese comics to convey various elements of the story.
Yes, manga often uses kanji. It's a common part of the Japanese writing system.
No, Senjumaru doesn't use Bankai in the manga.
I'm not sure. Maybe you should look for some of his works to find out.
Overall, the ending of Sakura Tsuushin manga ties up most of the loose ends. The relationships between the characters evolve in unexpected ways, and there's a sense of closure. However, some fans might have wished for a different outcome.