How BTC's price change? What are the factors that affect the rise and fall of the BTC?
Bitcoin prices change based on how the demand for bitcoin is going. Since supply of bitcoin is fairly constant considering the low and controlled inflation rate in bitcoin, demand is usually all we need to worry about.
Obviously this demand is shifted upwards when there are good things being said about bitcoin in the media, and demand is shifted downwards when bad things are being said.
When bitcoin gains enough adoption the price shouldn't even matter - people will view value in terms of bitcoin, not fiat.