1) Use the Vertice tool and highlight the objects with it, then push delete. (Also, you can uncheck everything from the Display window except objects, then do CTRL+A & DEL, to delete all of the objects.)
2)In the scenery window, there is an option which contains 3 choices (back, middle, front). Back puts scenery behind players and polygons, middle puts scenery behind polygons, but not behind player, and front puts scenery in front of everything (players, polygons, objects, etc..