By group instances, do you mean team instances? If so, in Chapter 2 you can get better ninja tools, like the Puppet Mask and Huge Blade of Konoha, and they provide better stats than their green colored counter parts. The color also tells you how high you can level it up. Green colored gear can be leveled up 3 times and blue colored gear can be leveled up 6 times.

Actually, Group Instance is where you grab a team of 3 people from your Group and challenge 3 waves of enemies. As far as I know, the rewards you earn from 2 stars are double that what you earn from defeating the 1 star Group Team Instance.

Oh yeah! I remember! I get those confused a lot. Reading words and comprehending them are not something I'm good at haha. Thanks for the correction.

he asking about the chapter 1 and 2.. not about the stars.. nothing special.. same rewards..