HIL Simulation Firmware Error

I have an APM 2.5 and also have an APM 2.8, and I am trying to do HIL simulation. I have downloaded FlightGear 2.0, Mission Planner 1.2.98 and connected the APM with USB cable and also have the APM connected to the radio receiver.
I am following the tutorial: http://ardupilot.org/dev/docs/flightgear-hardware-in-the-loop-simulation.html
When I try to download HIL Simulator for Planes firmware it gives an error “Bad Firmware”. Why?

Check that you can actually stuff 2.8 into APM2.5. There is a version limit beyond which the APM codebase doesn’t fit. I don’t know what it is off the top of my head though.

When i click ‘Pick previouse firmware’ it gives this error

My problem is solved now. What I learn is that HITL simulation firmware is not available anymore. So I did the SITL simulation, this is the tutorial i followed https://www.youtube.com/watch?v=3XjaxuAOyYI&t=49s