Coke. Always coke.

And there are things that don't qualify as "cokes", as a matter of fact. Slice, Fanta, Shasta, Miranda, Crush, and other fruit-flavored sodas should not be considered "coke", but rather, "soda", because that's what they are. It still isn't technically wrong to refer to one as a "coke", but it's not the preferred label.

It would technically be correct to refer to everything as "soda", but definitely not "pop".
Yes.