「～もの、それは…」 Atypical sentence structure?

Question

In this paragraph:

今から約20年前、携帯電話は日本ではほとんど普及していなかった。当時小学生だった私が、憧れていたもの、それは携帯電話ではなく、ポケットベルだった。

1. Does this paragraph look natural for a native to write?
2. What does もの mean in 憧れていたもの? Is it talking about a physical thing?
3. In それは携帯電話ではなく, why is ではなく an adverb, why not ではない(verb)?
4. Does the bold part translate to: "At that time I was a student but, there was a thing I wanted, that thing wasn't a cellphone, it was a pocket bell."

Answer 1

1. Yes it's perfectly natural.
2. Yes it's 物, a physical "thing."
3. This なく is a 連用形 (continuative form) of ない, and it can join two clauses. See: なく vs. なくて and stem form vs. てform as conjunctions and Connecting phrases with the stem of masu-form
4. The literal translation would be as follows. Don't be deceived by the first comma; that が is the subject marker. See: Reason for placing a comma between the subject and verb in this simple independent clause? In this case the comma was inserted simply because the subject part (当時小学生だった私) is a bit long.

   【｛（当時小学生だった→）私が憧れていた→ ｝もの 】、それは携帯電話ではなくポケットベルだった。
   The thing I, who was an elementary school student at that time, longed for — that was not a cell phone but a pocket bell.

Answer 2

1.Does this paragraph looks natural for a native to write?
Yes. There is nothing wrong with this sentence.

2.What does もの mean in 憧れていたもの? Is it talking about a physical thing?
Yes. もの can be translated exactly as a "physical thing".
http://dictionary.goo.ne.jp/je/75561/meaning/m1u/%E3%82%82%E3%81%AE/

3.In それは携帯電話ではなく, why is ではなくand adverb, why not ではない(verb)
According to "A Dictionary of Intermediate Japanese Grammar", page 211:
なく: a continuative form of ない used in written Japanese (to indicate a reason/cause for what follows if ない is attached to adjective) and contrast if it is attached to noun+copula.

Instead of なく you can also say なくて. Te-form is also used as a continuative form.
ではない can only be used at the end of the sentence or before a noun.

4.Does the bold part translate to: "At that time I was a student but, there was a thing I wanted, that thing wasn't a cellphone, it was a pocket bell."
当時小学生だった私が、憧れていたもの、それは携帯電話ではなく、ポケットベルだった。
I, who was a primary student at that time, was in love not with cell phones, but with beepers.