Only if river was part of the name (e.x. Tigris River) but if you are just talking about a river, then no.
no
You mean if you are writing out the number like "thirty-five"? No. You don't capitalize it in the middle of the sentence.
No.
no
No.
No.
No you don't.
Yea
No it shouldn't be capitalized.
No you don't.
In the middle of a sentence, you don't capitalize second floor.
Yes, you should capitalize the first letter of a quote at the beginning of a sentence, even if it is in the middle of another sentence. This helps to indicate that the quoted material is beginning.