So finally a success story!
The firmware that works with the Android app is the GitHub version one
Now the problem is that you have the older board (guessing because you connect BT to port #4) and I do not know if that accesses the Serial port in the same way. There is also
for your board but it might be some older version that will not work.
I suspect that the driver upload from the mobile app failed for you because you are using the older board. The tech support here is incompetent enough to not know .
BTW Scratch uses different firmware (though it uses a similar protocol so it might be an older version or something). The sources are packaged with Scratch and you can compile it yourself for your board.
For the record (if somebody has a similar problem) the app wasn’t upgrading the robot for me because of some problem in my phone. It worked well from my wife’s phone.
My current use-case mostly about controlling the robot over BT and, luckily, for that I can use the Scratch or mobile phone app firmware. I’ll use the same serial protocol that Scratch uses.