Indeed there is an issue while using the TrackBall in Chart with DateTimeContinuesAxis. I was able to reproduce this problem only on Android and logged a new issue
for this bug. Regarding that, you could keep track on the issue for further info and in the meantime, you could use CategoricalAxis as you suggested in your comment.
About the second question at this time, the TrackBall styling is not supported and for your convininece, I logged new feature request here
. You could review it and you could also add your additional info in it.