On the bottom of the bowl/carb you see that hose coming off of a brass fittng? That's the carb drain, on the same brass fitting is a screw that looks like the filter housing needs to be removed to access correctly. There's a fine slotted brass screw you undo in there to drain the carb. Use a proper screw driver or you'll booger the screw head up. Another option is to pull the feed hose to the carb and just run it till it's out of gas. Air mixture screw is behind a cap located on the same side of the carb as the idle adjustment. See that big round indentation on the left side it's in there. I use a 1/8in drill bit to drill a hole in the cap then use a hook n pic to pull it out.
G the air mixture screw is behind that square black plastic cap next to the O depression. Never seen one like that before. Had to use 200x zoom to verify in the pic that the O depression is not it, no brass cap in there.