no
Yes, it is correct to use a capital letter after the comma in "Dear Sir" as it is used as a salutation at the beginning of a letter or email.
It would be appropriate to use a comma between compound subjects or compound verbs.
Usually not, but it depends on context. There are no words that are always followed by a comma. You should concentrate on the use of verbs for a while.
Compound or not, never separate a subject from its predicate with a comma.
not if inc stands for including- it should be a full stop "." to indicate abbreviation and then continue sentence without a capital letter on the following word
A comma is not required in the salutation of an editorial letter. You can use either a comma or a colon after the recipient's name. For example, "Dear Editor," or "Dear Editor:".
If it is a business letter, don't use the th; use the comma and year. That way it is absolutely clear.
In that situation, the comma is optional. I would put one, because it makes it easier to understand the meaning at a glance, but it is not required.
It is almost always a comma, but rarely I have seen a colon. When you are writing a formal letter, it is a comma, but if you were to write a informal letter to a friend, it doesn't really matter. For all of the letters I write I use a comma, and so does everybody else I know.
Capitalize after a comma when it occurs within a sentence if it is the beginning of a new sentence or a proper noun. For example: "John went shopping. He bought a new shirt." or "I visited Paris, France, last summer."
do you use a capital letter for the word knighted
You typically use a comma after "Sincerely" when closing a letter or email. For example, "Sincerely, [Your Name]." A semicolon is not used in this context; the comma is standard for formal correspondence.