Arduplane4.3.5_SpeedyBeeF405WING_bl.hex: This is a complete firmware file with a bootloader. To flash this firmware onto the flight controller, you need to use the INAV Configurator software and enter the Device Firmware Upgrade (DFU) mode on the flight controller for flashing. Once the flashing is complete, you will need to reboot the flight controller.

Arduplane4.3.5_SpeedyBeeF405WING.apj: This is an ArduPilot JSON firmware file. If your flight controller is already running ArduPilot firmware, you can use the MissionPlanner software to load the third-party firmware and perform the flashing.

For AP4.3.X firmware, it is recommended to calibrate the compass on the flight controller. 
Calibrating the compass can improve the attitude stability and accuracy of the flight controller. When the flight controller firmware is AP4.3.X, you may encounter the switching phenomenon between "EKF3 active" and "DCM active" reported on the OSD. When the flight controller experiences significant vibrations, it can cause erratic attitude behavior, which may lead to a loss of control in autonomous flight modes. To avoid this situation, two methods have been found effective through testing:

1，Use a GPS module with a larger ceramic antenna area (25mm) and a compass (away from magnetic sources on the airframe), and enable compass calibration for effective calibration.

2，If you do not want to use a compass, you can consider replacing the GPS module with an M8 or M9 solution with a higher refresh rate, and set the parameter EK3_GSF_USE_MASK to 0 (occasional occurrence, quickly resolves).

The issue may be resolved with the release of AP4.4 in the future.
For more details, please refer to the following link：
https://github.com/ArduPilot/ardupilot/issues/23224


Regardless of which solution you choose, it is recommended not to directly set the ArmingCheck parameter to 0. Instead, you can disable invalid fault reports, such as logging fail due to the absence of an MicroSD card or compass warnings (compass not healthy) caused by not using the compass.

After completing the compass calibration and ensuring that the message report shows "EKF3 active," you can proceed with takeoff. Please note that before conducting flight operations, it is important to follow all safety procedures and ensure that you have sufficient knowledge and experience with the aircraft and flight controller.