QA-OBS-1: My drive ended up under a picnic table. Can I play from behind it? On top of it?
In general, no. Picnic tables, along with any other park or course equipment, are obstacles on the course. They are to be treated as any other obstacles, for example a bush or a tree. How you play your next throw depends on the picnic table. If there is room for you to take a stance under it, even by sticking your leg underneath, that’s what you do. If your disc is on top of the picnic table and there is room underneath, it is a lie above ground and you mark directly below it and play from there. If the disc is on top and there’s no room underneath (for example, a solid picnic table), you play from on top if that is reasonable. Otherwise, the table is treated as a solid obstacle and you mark behind it on the line of play.