Does anybody know how to reset passcode (for future situations)

You cannot reset a passcode unless you know it and can access the device. If you don’t know the passcode, then you can only restore the device to remove the passcode and set it up again.

Link-> If you forgot your iPhone passcode - Apple Support

Link-> If you forgot your iPad passcode - Apple Support

Link-> If you forgot your iPod touch passcode - Apple Support

If you do know the passcode and can access the device, you can go to Settings->Touch ID / Face ID & Passcode->Change Passcode.

Hello

First, head to Settings and scroll down until you find Touch ID/Face ID and Passcode. Select Change Passcode. This will prompt you to set a type a new passcode, and will require you to enter your current Passcode before changing to a new one.

Hope this helps.