Doe, John A., M.D.
No a greeting. A salutation is what you write at the end of a letter.
A resume is not actually a letter, hence it doesn't require a salutation. You can, of course, also write a letter to a specific employer, to which your resume can be attached. In that case you would be using a normal business salutation, Dear Sir or Dear Madame as the case may be.
To address multiple doctors, simply pluralize the abbreviation for doctor. For example, you would write "Dear Drs. John, Bob, and Sara".
yes
You could go with "Friends:" or write "hey everybody!"
It is like a doctor but someone who can help you
Write your memo on company letterhead. List the departments or individuals you want to address. If it is to the entire company, state that. Write what you need to say, and if it is a new policy state the date it will take effect. Write a salutation and sign your name and your position below your name.
Use the name of the person who wrote the letter, and write a formal letter. Use the salutation "Dear Mr. ____" or "Dear Mrs. _____" as a salutation.
The appropriate salutation depends on whether you also are a solicitor in your own country. If you are a female attorney too, then the appropriate salutation is "Chère Consoeur". However most French lawyers use the "Cher Confrère" salutation regardless of the gender of their interlocutor. If you are a man, you can write "Cher Confrère". If you are not an attorney, then the appropriate salutation always is 'Cher Maitre' or simply "Maître".
The doctor replied, sorry I can't chat now, I have a patient to see.
a comma, unless you write "To whomt it may concern", then you should put a colon (:)
If it is clinically indicated, a doctor will write a prescription for a wheelchair.