We all know that bitcoins price changes quickly because of its demand So if some online shop sells products and pricing it in bitcoin,
How can we price it ? Should the price change also like btc?
You don't need to constantly change the price. The best thing to do is set a price in fiat currency so it won't fluctuate much. Then if somebody bought your goods then he should send bitcoin that is equivalent to the price of the items. For example you are selling an apple for 2 $ each then the client will pay 2$ worth of bitcoin.