Yhu probably said something and it wasn't the truth so that's why he called yhu a liar
Juliet is saying that beggers cant be choosers basically, that there is no need or reason to brag but to just be humble and kind.
He meant that "I havent gone to school for more than six months for as long as i lived. but as early as i can remember, when i was a child if anyone spoke to me in a way that i couldnt process, i would get angry.
Personal pronouns, "I, I'm, I'll I'd" etc. must be capitalised. As for the middle of a sentence, I'm contains "I" and so therefore it is capitalised.
