Wild that Orochi has never been in any cover. And will remain so to the end.
Orochi along with Big Mom were very close to appear on the cover for volume 103.
That's definitely the UGP background, it should be in one of them. But if we assume the earliest it could have appeared was when Garp and Dragon were established as Luffy's family in volume 45, that's a lot of volumes to check, so you might have to do that yourself…
...is what I was going to say, but I halfheartedly opened a couple at random and was lucky enough to find it on page 212 of volume 47.
Awesome! Thank you for finding the source.
Simple. Because that's too many pages for the episode to cover.
I don't see it happening. In all likeliness, the end of chapter 974 is going to be the halfway point for episode 977.
If they don't drag out certain scenes, then I think they could possibly end the episode with the Kanjuro reveal.