3.1What is stored is what it takes to run an account and to answer hosted DNS.
3.2A hash of the account token. The token is shown once. It is not stored in the clear.
3.3Optional TOTP, encrypted, if enabled.
3.4Hashes of API keys and of session cookies.
3.5Which names an account owns, and the records published for those names.
3.6Plan, trial and paid-until, prepaid balance, and invoices: coin, amount, receive address, confirmation state.
3.7Whether a domain may appear in the public header.
3.8DNS records exist so the nameserver can answer them. They are the zone as edited. They are not a log of who queried that zone.