About registration and two-step verification
What two-step verification means for your HiYou account, and how it differs from App Lock.
HiYou's "two-step verification" refers to the two steps used to register or sign in: entering your phone number, then entering the six-digit SMS code sent to that number. There is no separate PIN or password step beyond this.
Signing in on a new device
Re-registering your existing phone number on a new device uses the same two steps. Entering the correct SMS code signs you straight in - there is no additional PIN prompt, email fallback, or waiting period. Keep your SMS codes private, since they are the only thing protecting your number from being registered elsewhere.
App Lock is a different feature
HiYou also has an App Lock PIN, found under Settings > Privacy. It only locks and unlocks the app on a device where you are already signed in - it does not protect your phone number from being registered on another device.