show hints of private test cases in missions

The private cases' hints were not shown previously.
Style/AndOr: Use `&&` instead of `and`.<br>Style/SpaceAfterComma: Space missing after comma.<br>Style/SpaceBeforeBlockBraces: Space missing to the left of {.<br>Style/SpaceInsideBlockBraces: Space between { and | missing.<br>Style/SpaceInsideBlockBraces: Space missing inside }.