theoretically yes, but there's a chance you might raise too much energy that your body is not used to (i have a friend who opened them all at once and they could not sleep properly for the next month)
i would personally recommend one per day if you're just starting
Yes, you can. However, when new to meditations, it can be beneficial to focus on one chakra per day to establish a better energy circuit within that chakra, and to avoid overstimulation.