At the moment, it's unknown if Gojo will come back to life in the manga. The storyline could take various turns and surprises are common in manga. We'll just have to wait and see.
Sure, Gojo came back to life in the manga. It was a surprise for many fans and was handled in an interesting way. The author crafted a storyline that made his return plausible and engaging.
I'm not sure. It could go either way. Sometimes characters come back in unexpected ways in manga. Maybe there'll be a twist that brings Gojo back into the story.
Toge Inumaki is important too. His special cursed speech ability makes him stand out. Also, the principal of the school, Masamichi Yaga, is likely to be important as he is in a position of authority and has an influence on Gojo and the other students. There could be other characters like the members of different clans that also play roles in the complex web of the story.