1)The establishment cause is when religion or anything political is not mixed together for there not to be any issues or indifference among the two. The relation it has with “Lemon test” is that it make sure all religion has its space and different freedom amounts both.
2) Yes, burning the American flag is protected by the first amendment as a way of freedom of speech. It is also known to be a symbolic speech agreed by the supreme court although it can cause issues by the Americans beliefs.
3) When someone says ” I’m taking the fifth” is more as saying I will be not speaking anymore. You will like to remain silent or you just don’t want parts in the situation. It can also be a way to prevent yourself into getting in a forceful argument between your freedom or accusation.