See about here about rebinding controls: https://github.com/nothke/shakedown-docs#rebinding-controls
For reverse you have to go down in gears, by pressing "<" by default. I will add automatic reversing when stopped and holding back in one of the next builds.
I cannot reset to nearest track point yet, but you can press F to unflip if you end up upside down.
The new build will have persistent best times. Coming hopefully today.