Could one use "...de ĉiam" instead?
I disagree. "De ĉiam" answers the question "de kiam?".
Since when? Since always.
Vi ne konas mian forton.
Presumably the English version is talking about parallel universes: "of all times". Does that also apply to the Esperanto version?
So, would "of all time" be "de ĉiu tempo" or was the English version just a typo?
For more discussion see the following threads.
ci ne estas should be accepted too.
Hardly, as pretty much no one uses ci and its use is not recommended. Just use vi.
sorry but some people use ci. and it's recommended by common sense. use ci for singular form, please.