Kriya Yoga Q&A - Questions on Kechari, Kriya Initiation, Guru Pledges, Lineages and Vedic Astrology

Responses to the Following Questions:
1) I have heard, that meditation in a dark environment can be beneficial, is this actually helpful, or does it matter?
2) What is Kechari Mudra? Is it necessary?
3) Ryan, have you ever heard of people practicing pranayama and experiencing headaches, dizziness and so on?
4) What happens at a Kriya initiation? Does one have to pledge
allegiance and devotion to a guru, such as Yogananda? What happens
if you don't? Is there a consequence? Do you somehow lose out on the
full benefits of Kriya?
5) Is it possible to receive Kriya initiation in some way other than
in person? Maybe via telephone? Or Skype?
6) Is it okay to read the writings and books of the many different
teachers? Yogananda, Daya Mata, Donald Walters, Roy Eugene Davis,
etc. Are they different or the same? If you read them all, will you
become confused? Do different people teach a different form of
Kriya? How are they different?
7) If one reads the works of the teachers from India (Lahiri
Mahasaya, Sri Yukteswar, etc.) haven't most of them been translated
into English from another language? Does something get lost in the
translation? Have their followers reinterpreted and modified some of
the core teachings and ideas? As Kriya passes from teacher to
student, are small changes made in the practices? For example, when
Yogananda came to the USA, did he make changes to what his teacher
taught him, so that it was easier to explain Kriya to westerners?
8) Does involvement in Vedic Astrology enhance the practice of Kriya
yoga? If one does NOT follow / understand Vedic Astrology, does one
lose out on some of the benefits?