V0.8b shouldn't have any major bugs/errors. If you are having "NOT IN LIST" errors show up, it's VERY likely that you are using a save that was BEFORE they became transferable to new releases.
When a new version is released, the variable "current_version" is checked, and if it is NOT equal to the latest version, it updates the quest dictionary. Saves from before V0.6.2 do not have this variable, and is defaulted to the latest version, thus not updating the quest dictionary unless you manually change the variable with some ren'py dev tools. Though I would suggest using a save someone has provided or start a new game as some items may not be rightfully defined and you may run into errors there.
TL;DR: Either use a save from V0.6.2 or later OR start a new game.
And about the question above, yes, Melissa will have new content on V0.9. I'm currently working with her now.