The first (unnumbered) three are fine. 1. is incorrect. 2. is correct.
"He is Turkish origin" without the adjective is "He is origin", which equates a person with an abstract noun "origin". That doesn't make sense. It's like saying "He is destination" or "He is comprehension". 'of Turkish origin" means "from a place in Turkey, originally". A Turkish-American, for example,
He = noun (subject) is = verb Turkish = adjective modifying "origin" origin = noun - (predicate noun)
Leaving out the "of" (preposition) is incorrect, of course. Compare:
He is from Turkey. [correct] He is Turkey. [not correct] She is in the kitchen. [correct] She is the kitchen. [not correct] We are of a different opinion. [correct]
I surmise that Andrei has seen a sentence like "We are the same age." Here, "we" can't equate with "age." Still, there is no "of."
So, I would add a little more to CJ's explanations. When you are talking about numerical concepts like age, size, weight, and height, "of" is optional. Yet, I feel that in these concepts, the deletion of "of" has gained currency for the sake of lin
Now that you mention "same", I think I should agree with you. We don't take "of" out of "We are of an age."
With regard to your questions about the acceptibility of the "different" examples, I am very cautious of answering them. I am a non-native speaker. I had never been in any foreign countries in those English-learning years. But I am honore
"We are the same age" - nowadays people seem to prefer this form (at least in speech) to the traditional form "we are of the same age". But why can persons be an abstract concept "age"? I looked for the origin and the logic of the construct of this kind but it was vain efforts. Only one phrase I found in the OED and I feel to be related with this usage