to sell / promote something at a higher value than it is supposed to be; it describes people who become difficult / picky, or want more benefits, because they suddenly become more popular
literally, the mountain is high, emperor far away, he cannot control. nowadays, it means far away and unreachable by the central government (management); it is difficult to get justice
to describe the action of someone who exposes all their private matters / secrets for all to see and not caring whether other people actually want to know about it or not.