In the manga, Senjumaru did not employ Bankai. The character's abilities and actions were depicted differently without resorting to this particular power.
Shinji did use his Bankai in the manga. It was a crucial moment that turned the tide of the fight. The Bankai's power and unique abilities were showcased, adding an exciting element to the story.
While hydrogen peroxide can potentially help against mange, it's not a guaranteed cure. The severity of the mange infestation, the type of mange, and the animal's overall health all play a role in determining its effectiveness.
It might work to some extent. Hydrogen peroxide can have antiseptic properties, but its effectiveness on mange depends on various factors like the severity and type of mange.
You need to be careful when using borax and peroxide. Mix them in the right proportions and apply the solution carefully to the affected areas. But always consult a vet first.