nitrous oxide cylinders are blue
Nitrogen is N, and since the Oxygen bit is in oxide, it's O2. NO2
The color code for medical gas cylinders containing nitrous oxide (DA) is blue.
up up down down left right left right BA BA
there is no code
No, this compressed gas has a long, long shelf life. But the cylinder it is smooshed into has a code date on it. Under nominal storage conditions, it should last decades, but corrosion can affect the cylinder or the valve. And should the tank be emptied, it cannot be refilled if the cylinder's "useful life" has passed. It will have to be hydrostatically tested and recertified. We know that nitrous oxide (N2O) is pretty stable stuff under nominal conditions. It stays the way it is when it is bottled up.
Sorry but no
Only the sulphur dioxide is largely used (code E220 in EU).
Runaway slaves didn't have code names.
The code is ITO (but this is not a true chemical formula); this is a mixture of In2O3 and SnO2.
Code
There were many code names. The Operational code name for the invasion was "Overlord".