Not if the Passkey was synced (ex: you used iCloud keychain). If the passkey was not synced, then I would have to assume it would be the same if you lost a physical hardware key.
How do you access iCloud without your passkey?
Call Tim, he'll vouch for you.
I use a yubikey. But AFAIK, Apple doesn't actually use passkeys for iCloud/Apple ID authentication.
Not yet, but Google wants them to become ubiquitous. So in that (far) future, backing your passkeys up in a cloud (that is also protected by passkeys) doesn't help
Apple account recovery supports setting a recovery code or having a friend listed as a recovery contact.
Apple does not yet support Passkey for iCloud accounts login.
Complain loudly on Twitter and hope your tweet goes viral.