k_passwd

— Microsoft account — avoid. Favor local account. So much simpler.
Microsoft account login and preferences are saved online and the synching is unreliable and not simple/straightforward.
— rename login .. poorly implemented. Folder name etc are unchanged. https://superuser.com/questions/371382/where-is-username-variable-defined explains some registry settings that are not updated consistently.

Based on this experience, I would never rename a login name in windows10. I’d rather remove the misnamed account and create a new. Note you may need up to 1GB just to create it.

== password hint — is more practical than password recovery question. (Therefore, I pick random questions and give rubbish answers)

Note password hint is only accessible in ControlPanel not the new interface 🙁

Warning: this feature doesn’t work on the unlock-screen

Sugg: You can jot-down the same hint on paper as reminders.

— If I need to give password to my son, I usually change it to a “safe” value and rely on password hint.