>>23471575
There's been a few for key moments, but unfortunately only for in-series characters - no crossover CGs so far (I don't think there'll be any)

>>23471566
Start of Chapter 3 via a Side Mission oddly enough & no, you don't fight him at all. I'm kinda surprised he joined up that early... makes me wonder where game will go.

>>23471578
I think the only Getter-related villain I encountered so far is some Wukong-esque character. I forget the name; not the most familiar with Getter Arc sorry.

>>23471583
Still fairly early on - I got the Destiny itself via an early unlock of getting Shinn to a certain score to unlock an optional mission to receive it early along with Lunamaria