What are the classification of dangerous goods as per IMDG code ?

Class 2: Gases

Class 2.1: flammable gases
Class 2.2: non-flammable, non-toxic gases
Class 2.3: toxic gases

Class 3: Flammable liquids

Class 4: Flammable solids; substances liable to spontaneous combustion; substances which, in contact with water, emit flammable gases

Class 4.1: flammable solids, self-reactive substances and solid desensitized explosives
Class 4.2: substances liable to spontaneous combustion
Class 4.3: substances which, in contact with water, emit flammable gases.

Class 5: Oxidizing substances and organic peroxides

Class 5.1: oxidizing substances
Class 5.2: organic peroxides