The second half of video (without subtitles) demonstrate how chakra are activated by vibrating them with mantra which have different resonance frequency and outcomes of activating chakras
Not everyone will have magical powers at the moment when the third eye is opened. There are also some people who need to experience the situation you said before they can grow.
Not yet, even if the third eye is opened, there are still some processes that need to be experienced before you can truly understand what you are saying now.