This is a common misconception. The experience of an "open" crown chakra is actually the brow chakra connecting to the crown. When Kundalini pierces the crown the soul in human embodiment is completed, fulfilled, perfected, permanently united to the cosmos - and all the chakras below are immediately fully opened and perfected. And the human experience becomes SATCHITANANDA - freedom from illusion, mergence in pure consciousness, and bliss. All that keeps the soul connected to the human body at this stage is a desire to help and a love for others still stuck in the chakras below.
There is nothing wrong with using spiritual practices that purport to "open" the crown chakra, as these will facilitate the opening of the brow. However the piercing of the crown is a gift of grace from the Universe, from the Divine, not an act of will by the individual soul.
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