The firmware's name, version and source revision

ArduPilot says what it is: the vehicle type (ArduCopter, ArduPlane), then the version as major.minor.patch, then in brackets the first eight characters of the git commit the firmware was built from. “-dev”, “-beta” or “-rc” after the version mark a build that is not a stable release. Words between the version and the bracket were added by whoever made a custom build. Two firmwares with the same hash come from exactly the same source code. The line is sent each time a ground station asks for the parameters and written at the top of every log.

When you ask for help, give this whole line: version and hash say exactly which code you fly. The Firmware Inspector reads the same out of a firmware file.

Where to do it:Firmware InspectorFirmware Builder