well, it only took an hour of deleting files, changing file permissions, manually running pip to upgrade python package versions, pulling the latest version and other assorted yak shaving tasks to renew my certificate -YAY!
It did make me update the challenge response on my website for some reason, but oh well…
You can prevent certbot-auto's self-updating behavior with --no-self-upgrade. There is no downgrade feature, but you could get an older version via the version history on GitHub.
The reason for that is that ACME challenges are authorization-specific, not domain-specific. The challenge is different every time you receive a new authorization. Currently, I believe Let's Encrypt authorizations last for either one or two weeks.