You underline or italicize them.
Yes.
Only the word English is capitalized. History should not be capitalized. Example: English and history are the subjects that I love.
In the middle of a sentence, you don't capitalize second floor.
No they shouldn't be capitalized.
No.
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
All words are capitalized at the beginning of the sentence including am. Example: Am I the least to know about her?