The design would be better suited to some kind of walking device.
This however is supposed to fly :
My robot hovers using compressed air from an on-board air tank
An air tank such as a diving cylinder certainly contains enough air at sufficient pressure to take off like a rocket. So in priciple you should be able to make something hover at least for a while. He has not specified what height the robot needs to hover at. By putting a skirt round the device you would get a hovercraft which could provide quite a bit of lift and would avoid the problems of keeping the thing stable.