Hey there!
Let me see if I can clear things up a little bit 
When you pedal backward, your power drops to zero for a duration of time. During the time that you are backpedaling, the prescribed power is not zero. Typically it is a recovery interval at around 60% intensity. By having these zero values in your workout, it will artificially increase your Normalized Power, as well as the Intensity Factor of the workout.
Firstly, if you dislike that it automatically starts, you can disable “Pedal to Play/Pause” in your TrainerRoad Settings. By disabling this feature, the workout will start and pause when you manually press “Start” or “Pause”. As for how to scrub forward or backwards, check out this Forum Post that summarizes the process for each TrainerRoad Device:
For now, there is no way to swap out planned rides added to your Calendar. However, you can assign a completed ride in place of a planned ride if you wish. For example, if you have a planned ride today, and you want to do a different ride instead, simply complete the “different ride”, and afterward, you can “associate” that ride with the originally planned ride. To do this, click on the completed ride, and then click the “Associate Ride” link. You can get a little more detail here in this article from our Help Center:
As for a resource to help you get the most out of Calendar, I would recommend checking out this chapter of our Help Center that is all about Calendar
I hope this helps, let me know if you have any further questions!