Discord later banned the account for violating the TOS when lying about her age and stated they would only restore the account if they shared a photo of the kid along with a copy of her birth certificate or passport. The father gave in and complied so she didn’t loose access to her friends.

This is valid on Discord’s part. The father should have helped her to make a new account instead of giving away records if he’s really insistent on letting his kid have Discord. Also, “loose”

Once you change your username, your old and new Gmail names will both work. In other words, you can use both usernames to sign into your account and send or receive emails.

This is just an email alias, not an actual change