Ground Cable

The cable should have its insulation value imprinted on the insulation itself. You may confirm voltage and current capabilities relative to the type of insulation on the cable. Green should not be used as a feeder cable.

Generally No (certainly no if you are planning to use it on the high voltage feeders, eg- 1kV and above). Check your cable specifications for rated voltage ratings.

I am assuming you are NOT planning to use "green" coloured earth wire as a phase conductor (which is illegal in every country I can think of).

Consult your local electrical standards and/or cable manufacturer for more information.

It depends on the cable insulated material use, is this cable insulation's material PVC insulated , or is it XLPE insulated. Is it armoured as well. It will be fine if the material is XLPE material, however, when colour code is in concern, it might not be acceptable to be put to transformer use, unless it is use for grounding all the metal body parts of the transformer.

Like they said no. The insulation on the grounding wire is cheaper and biodegradeable usually.

In many countries (at least in ALL countries in the EU) ground cables HAVE to be green and yellow.
Green or yellow cables are absolutely forbidden for any purpose. (Except inside appliances and less then 50 Volts)

i wont advise it...as it always going to confuse you.