hello, can you please clarrify for me that if someone shares their save with me and they have all the achievements in the game would they all auto unlock straight away for me or would only the story related ones unlock? and i would still need to do the misc stuff such the zipline one, shooting a  bug and blocking ten attacks?

In my experience, I hosted a shared world after unlocking every achievement in that world. When my friend came in, none of the achievements unlocked for them. Maybe I just did it wrong, but it didn’t work.