What contet is new compared to the v.17?
I have noticed only spider lady in v0.2 but there is no way to go past her after receiving gold from chest.
Are any of the old main cast characters besides Phoebe back already ? (Like Ivy and Carmen)
...I know I'm replying to month-old posts, but these are legitimate questions regardless.
Long story short, though? No, the other main characters have not yet been brought back.
They overhauled the game back in 2020 (v0.12) after the original game (everything up to v0.1155) got shut down after the devs received a cease-and-desist letter over all the pokémon content. But even after four years, they have yet to add in anything more from the original main quest than Phoebe.
OTOH, the devs
did add in a lot more side content, as well as a lot more content in general. Phoebe's plotline is vastly bigger in the post-overhaul versions than it was in the original version of the game. The Phoebe-related updates alone took about a year (late 2021 to early 2022). The devs have clearly gotten a lot more ambitious.
From mid-2022 'till now, the devs' focus has been entirely on side content (the punk cosplayer and her gang/band, the mailman cosplayer, the totally-not-Yor-Forger cosplayer, etc.). But IIRC they did say that Ivy was going to be their next big focus, and the Scarlett-and-her-gang side plot seems to be mostly wrapped up now.
With a little luck, we just might see the first Ivy updates before the end of 2024. But that's a big if, though. And we'll be lucky if the main plot is finished before 2030...