Neither of these work. iCloud Recovery lets you restore deleted notes (if you're lucky), but not get back a note where you've accidentally deleted the text. Getting back a deleted note is easy; you can already do that from "Recently Deleted" for up to 30 days. But undoing a stray edit, you'd better do it right away.

e.g. you're trying to copy text out of a note so you select a portion of it. One stray tap and the highlighted text is gone. Shake to undo immediately or the text is long gone and then it syncs everywhere. The maneuver is so risky I've taught myself a work-around when I'm on my iPhone when I only need a portion of a note. I use the share icon to copy the entire note, paste that into a new temporary note, edit the new note down to the portion I want to share, then copy that text and finally delete the temporary note.

Locking a note doesn't do what you think it does. It doesn't prevent edits. It just means you need to provide a password to view the note. Once you've unlocked the note, it's just as susceptible to a stray edit.

On macOS you can really lock files, preventing them from being edited:

https://support.apple.com/guide/mac-help/lock-a-document-on-...

It was silly of Apple to use the term "lock" to mean different things. They should've called the thing in the Notes app "private" or "hide" or something. Also, locked notes don't have the same functionality as non-locked notes; e.g. you can't add attachments to a locked note:

https://support.apple.com/guide/notes/lock-your-notes-not28c...

Anyway, the best you can do if you accidentally edited a note and didn't undo it in time is to extract the note from a backup of the Notes sqlite DB, should you have one from your Mac (say).