Need help with ETTLand multiple remote flashes

Appreciate some help on a few questions on Canon ETTL and mutiple flashes

A) I understand for Canon ETTL group C is metered differently from the both Groups A and B but does that mean that if I set the FEC for the master that would mean both Groups A & B are set to the same FEC? or do I have to set FEC for both A & B separately.

B) Following on from the question above does it matter if I set the ratio between Groups A & B ie. would it use the ratio and then apply FEC to both Groups A & B?

C) If you set FEC and the flash goes into auto off are the FEC settings lost?

D) If you set groups A, B, C with all the ratios and FEC and Group A fires but Group B does not it affect the output of Group A ie output of A increase to compensation for lack of Group B?

A) The difference between Group C and Groups A and B is that Group C is not used to determine the exposure of the shot. Only Groups A and B are. When you set the overal FEC via the camera or the master flash, all the overall lighting is changed proprotionately so that the A:B and C ratios are still maintained.

B) As mentioned in A above, the ratio of A and B and maintained even though the overall intensity of the combined lights are increased or decreased by the FEC.

C) No, assuming by "auto off", you mean the flashes go into sleep mode.

D) No. Group A output will be the same whether Group B fires or not. For example, if A:B is set to 1:4, if Group A fires but Group B does not, the exposure will be underexposed by two stops.