Why is yoga so valuable as a spiritual and life changing process? What is kundalini and why is release of kundalini so valuable to life, manifesting, and divinity?
Kundalini is consciousness stored and power or energy. Kundalini in the non awakened state resides in the base of the spine at the first or base chakra. Sitting there it swirls around mostly being awakened during sexual intercourse or manual stimulation.
During higher awakening the kundalini can open and move out of the first chakra moving up through the other chakras. In this way kundalini passes through 1st, 2nd, 3rd, 4th, 5th, 6th, and up to the 7th chakra. When the kundalini or conscious energy (power) moves through (meditation and pranayama or mastery of breath are two great ways to raise kundalini through chakras) chakras passing energy up through the metaphysical storehouses (chakras) of power, spirituality, metaphysics and divinity.

Kundalini Chakra
In this way by practicing kundalini, Kriyas or pranayama one may open, clean, and energize chakras, releasing the metaphysical properties inherent or stored in the true value of the chakra.
Remember chakras are for things metaphysical (clairvoyance, clairaudience, clairsentence, as well as intuition, things like achieving desires, teleportation, longevity, realizations, power, fame, fortune, or even deathlessness) and non metaphysical (non-spiritual: health, beauty, constitution, cleanliness, graces, wisdom, alertness, healthy organs, and even intellectual ability).
With this in mind it should be understood that kriyas or pranayama practiced everyday in the way of mastering AUM and Samadhi is the best way to open, activate, and power kundalini, chakras, and metaphysics.