You underline or italicize them.
Yes.
Yes, you should capitalize the words "English" and "History" in this context as they are specific subjects in this case.
In the middle of a sentence, you don't capitalize second floor.
No.
No they shouldn't be capitalized.
No, you would not capitalize either word in this sentence
The way you capitalize other words. If it's at the beginning of a sentence it should be capitalized. If it's not then it shouldn't be capitalized.
Only capitalize 'spelling' if it is the first word in a sentence.
It depends on the sentence. It can mean any of the following words: what, which, that, who, than.
In most quotations you should capitalize the first word and the other words necessary; as in any other regular sentence. There is no need to capitalize most words just because they are in quotations.
Proper nouns
You simply capitalize the "am" as you would any other word at the beginning of a sentence. For example, "Am I late?"