iCloud temporary (or alias) emails are a feature of Apple's Hide My Email, and they’re tied to your Apple ID. Here’s how they work and answer to your questions:
1. Can you use iCloud temp mail without a password?
No, not really. You need to be signed in with your Apple ID to create and manage them.
However, once created, you can use the alias email to receive emails without needing a password for the alias itself.
If someone sends mail to the alias, it’s automatically forwarded to your real iCloud .
It works indefinitely until you delete or disable it.
It's not like temporary email services that expire after a few hours.
Key Notes:
You can manage aliases from Settings > Apple ID > iCloud > Hide My Email or via the iCloud website.