Yes, it is a basic principle of trading and investing. Buy low and sell high.
Yes! It sounds simple, but in fact, it is the hardest part. You never know when bitcoin reached its peak or hit the button so it's always a guessing game. And moreover, considering that bitcoin like any asset can go down because of the FUD, it's getting even harder to find a perfect moment to buy or sell. That's why we have DCA to solve this problem.