Yes it does.
For Example: Ralph H. White, M.D.
Source: http://new-www3.uark.edu/qwct/resources/handouts/33%20Commas--%20Almost%20Everything%20You%20Need%20to%20Know.pdf
Not necessarily. Commas are a feature of sentence structure.
No, before ... as in: Marcus Welby, MD
No, a comma does not go before the word 'in'.
Yes. You should write it at John P. Doe, MD
An comma goes before so
It could go either ways?
A comma is generally not needed before "because" in a sentence. However, if "because" is introducing a dependent clause, a comma can be used after it to separate it from the main clause.
Not necessarily. There is no word in English that requires a comma before or after it.
after
After
no
No.