I've created a child Google account by Family Link App then I remove it on parents' Android device. Then my child Android device was locked and need Family Link access code to unlock. But the child account was removed from Family group already, so

You can also use a parent access code to unlock your child's device. You get an access code in the Family Link or on the web. This number will not be sent via email or SMS. Enter this one-time use only number into the child's device before the cod

Parents can unlock on the child's device with a code created on the app on the parent phone or the parent can unlock the device from their own phone. When the device is locked, their child's phone will still be able to make outgoing calls to anyon