Not advisable.

Usually a ring circuit from 16A MCB will have 2 nos of 13A SSO. Unless you are certain about the power consumption of all the devices connecting to the extension cord power rating will not exceed the 8A simultaneously when used together with the refrigerator. Remember, refrigerator got rotating equipment (compressor ) which required higher ampere during compressor kick in.

Not accurate. It have yet to cover the worst case. Usually a 16A MCB will have 2 nos. of 13A SSO. Usually this 13A SSO will be installed close to each another. If the

1) 1st 13A SSO in used for the electrical kettle / oven
2) 2nd 13A SSO in used for refrigerator + the extension you use for another ( high power consumption device)

The 16A MCB will trip, if it did not trip/malfunction, the cable for this circuit will be melted /burned.

It has nothing to do on the material of extension cord. It start with the fundamental on how much ampere / kW the circuit can take from the 16A rated MCB.