I reflashed the boron with system1 binary file. Am i wrong to assume that this is the deviceOS running in the boron?
Have you also tried reflashing the bootloader via serial as previously mentioned? You didn't mention either way and if you haven't done that it's worth doing - perhaps part of it was overwritten in your previous mbedOS attempt.
It sounds like you were unable to get the bootloader flashed because you were unable to get into serial listening mode (probably because the bootloader is damaged). You should be able to do this with JTAG. This step will be essential I think. Someone more knowledgeable can hopefully chime in here, but essentially what you are doing is similar to this post, but please double check the memory addresses from the boron datasheet online.
Ok. For clarity, does this mean that the boron cannot support the mbed OS? Can it support the nrf52 sdk?
Officially none of the Particle products support an alternative OS. It's one of those things that may technically be possible, but once you start messing with the OS, it's kinda on you to figure out how to work with that. I haven't yet heard of anyone doing that (especially because the boron is super new), so I think you are in uncharted "maybe" territory here.
That said, we should be able to help you get the normal OS working again with enough information. Can you specify how you loaded the "ble program running on mbed OS" in the first place? What commands did you use to do so? What is the size of that code set? This may help us determine what might have been changed that needs to be restored. I still think the bootloader is your problem unless you've already successfully re-flashed it.