With these exact words, yes it is. But you could say "É demasiado cedo" (but never "é demais cedo" or "é cedo demasiado"). This in European Portuguese. Don't know if Brazilians use this alternate wording.
Yes, this applies for Brazilian Portuguese too. You can also use "demasiadamente", in the same place as "demasiado" (the latter is an adjective working as an adverb, the former is the actual adverb, and they both mean the same thing).
Portuguese "cedo" = "early", not to be confused with the Spanish "cerdo" = "pork".
@DeanG6, thank you. Good tip. I like to associate things when trying to remember things. Now I've just learned two words. 03/03/2017
Would "E demais cedo " be right too ? If not , is there a rule to explain where the adverb is placed in realtion to the verb ?