or whether you need to redo from beginning if you fall behind because AWS waits for nobody

Welcome Yin! Don't feel pressured to upgrade midway. We keep all the old versions of the site around — https://serverless-stack.com/chapters/changelog. That said, if one of the updates has something you want to learn, I'd recommend going through it from the start while skimming through the chapters that you are already familiar with.

Thanks Jay! Also one more question, do you guys prefer Slack threads vs. adding a new Slack message in channels? I think I almost got booted from one community because I didn't stick one way or another

People usually prefer threads. But the community is still fairly small that I don't think people will mind one way or the other. Though, if you've got a technical question that warrants some discussion, it might help to make it a thread so people can follow along with the conversation.