1. The maste comes back.

Question

2. A master comes back.
3. Master comes back.
(Are they all grammatical? Can we use as in #3? In #3, 'master' is used as a proper noun? Am I right?)

4. "Yes, master."
In the expression, 'master' is used in the vocative case. So we don't put 'the' before master. Is it right?
Or can we omit 'an article' before 'master'?

5. When did master lose Chuchu?
6. When did Master lose Chuchu?
7. When did the master lose Chuchu?
(Can we use all the expressions? #7 is no problem. What about #5? Can we delete 'the' before 'master' as in #5?)

Answer 1

1-3 are fine (correct the spelling of "master" in #1), and yes, in 3, "Master" is a proper noun.

4. Your explanation is all correct.

5. ... the master ...
6. OK as it is.
7. OK as it is.