I did the same thing, I shorted positive to ground accidentally.
I tried to get help here but nobody could really offer many suggestions. I did a lot of diagnosis and analysis and found that my IMU was fine but my main board had blown the PPM chip.
I ended up ordering a new main board from the store which USPS then lost.
I finally ended up ordering a new main board from a local supplier as I couldn't wait for the USPS service to finally get back to me. That was over a month ago, still waiting.
How did you reverse power the board, from the servo rail? If it was the battery input you may have fried the voltage regulator. If the servo rail then i don't think it would do anything. What do you mean it partially works. Is the power fried or not. You did look at the schematic, didn't you? !!!