"Dark Armed Dragon" cannot be Special Summoned from the Graveyard, even if it was properly Summoned beforehand.

Is it safe to assume that this ruling is the same if it is removed from play? Making it not able to special summon other than it's effect from the hand?

Yes, you are correct.

ah yes the classic "except by, only by" question. Yes that rule applies to the RFP zone as well.