Does a comma change the meaning of a sentence?

A. John said that he saw the police arrest the woman, of about 50 years of age.

1. Is sentence A correct English?

2. In A, is the comma (,) between "the woman" and "of about 50 years of age" correctly used?

3. Is the meaning of A a little bit changed if the comma is removed?

4. Is it okay to put a comma before a prepositional phrase when this prepositional phrase(=of about 50 years of age) adds its non-essential information to its preceding noun(=the woman) like in sentence A?

5. What do you think about my answers to the questions 1, 2, 3, 4?

(If A is wrong, could you answer about whether 4 is possible with an example?)

My answers

1. Yes, I think A is correct English.

2. I think the comma between them is correctly used because the comma seems to be added for indicating "of about 50 years of age" as non-essential information.

3. I think if the comma is removed, the meaning of A could be slightly changed because "of about 50 years of age" defines essentially who the woman is, unlike when the comma is inserted.

4. I'd say yes like in A.

Would you answer my questions separately?

Thank you very much!