1. There's no wiki (aside from a mostly-internal one used to track Aphrodisia world lore), but our Discord server has a quest-help channel for such questions.
2. Nope, you can migrate older save game versions back from the very earliest release. We try our best to make it so you are not forced to start over from scratch given how long the campaign is, though you may miss out on some minor content added in later. If there is ever a need to restart a campaign entirely, we'll be sure to announce it.