No, definitely not. In very many cases it would not even be optional. It would simply be wrong.
no. if but before is a sentence on its on and after but is a sentence on its own then put a comma before but.
befor
after
Before. ex. I had every intention of going to the store, but I forgot.
Yes, there is typically a comma after "third" when it precedes a list of items in a series. For example, you would write, "I have apples, oranges, and third, bananas." However, if "third" is used in a different context, such as "the third book in the series," no comma is needed. Always consider the sentence structure to determine comma placement.
Yes
No, a comma before "as appropriate" is not necessary. It depends on the context of the sentence and whether it flows better with or without the comma.
No, a comma does not always come before "for instance." It depends on the structure of the sentence. A comma is typically used before "for instance" when it introduces a non-essential or parenthetical element in the sentence.
No. There is no word in English that always requires a comma before it.
Sometimes, but not always. There is no one single rule that applies to "but." ----
Not at the beginning of a sentence. As you know is a clausal sentence adverbial, and as such it should generally be set off by punctuation. That would mean a comma after it at the beginning of a sentence, a comma in front of it at the end of a sentence and commas on both ends when it appears in the middle of a sentence: "He is, as you know, rather obstinate."
No
A period should come before the footnote at the end of a sentence, while a comma should not.
It depends on the type of sentence. So your answer would be not all the time. I hope that helps! :)
,Always.
When which is used to introduce a nonrestrictive adjectivial clause it must it must follow a comma. But there are numerous examples where which does not need to follow a comma. Including: Which melon do you want? I can't tell which melon to buy.
If a comma is needed, it normally comes after parenthesis.