Check the in-game badge panel
The supplied material does not record the Billy Badge’s exact requirement or reward. The game’s badge interface is the safest place to confirm the current wording.
Record the version
Updates can change how a badge is earned. If you are helping another player, include the game version and a screenshot of the badge description.
Avoid unsupported walkthroughs
A fixed step-by-step unlock route is not included because no verified source in the supplied material documents it.