This is an interesting question. It would be best to first clarify a few points you make before answering your questions.
You wrote:
A Human is identified in terms of 3 Bodies, 3 States and 5 Koshas or Sheaths. An Atman/soul covered by three bodies, Which are Karana sharira (Causal body), Sukshma sarira (Subtle body) and Sthula sharira (the Gross body).
The ‘causal body’ does not really exist on an individual level. There are 3 upadhis (not states as you refer to) that make the Atman appear to be something than what it is. These upadhis are the gross, subtle, and causal bodies. The causal body, however, exists on a universal level and refers to the collective maya out of which the universe is created – it does not exist on an individual level as the gross and subtle do. Sankara says “Avidya, or nescience, indescribable and beginningless, is called the cause, which is an upadhi superimposed on Atman.” (Atmabodha 13.) Sankaracharya describes these 3 upadhis in Atmabodha 11-13.
It is not a ‘human’ who is identified in terms of 3 bodies, it is the atman which appears to identify with the subtle and gross bodies as a result of the 3 upadhis. Out of the subtle bodies all living creatures are formed, not just human.
You wrote:
Where does a Soul attached to these Body?
Answer:
The ‘Soul’ when seen from universal standpoint is often referred to as the Atman. The Soul when seen from an individual standpoint is often referred to as the atman (small 'a' denotes the Atman in the individual). The individual jiva is Pure Consciousness limited by the upadhi of the vijnanamayakosa. It is also said to be the reflection of Pure Consciousness. “...(the individual soul) is intelligence itself.” (Brahma Sutras 2.8.18) The Brahma Sutras (2.8.19-22.) say that it is ‘atomic’ in size. It is said to reside in the cave of the heart (Brahma Sutras 2.8.24) - “He sees the Person dwelling in the heart who is supreme, higher than the individual souls” (Prasna Upanishad V.5., see also Chhandogya Upanishad VIII. i. 1-5.). The heart is interpreted to mean the buddhi, the intellect. The cave being the innermost part. See also Brahma Sutras 1.3.12-13 and 2.8.18-50. “Though all-pervading,...It is manifest in the buddhi…” (Atmabodha 16.)
You wrote:
Where and How does the Physical body, the Subtle body and the Causal body attached to each other? Specially attachment of Sukshma sharira (Subtle body) and Sthula sharira (the Gross body).
Answer:
They are not ‘attached’ to each other, one is enclosed with the others, that is why they are kosas, or ‘sheaths’, because they cover the Atman like a sheath. Each kosa is finer and finer. Each kosa permeates the more grosser sheaths. The annamayakosa (physical body) is the least fine so it does not permeate any other sheath. The pranamayakosa is finer than the physical and therefore permeates it. The manomayakosa is finer than the pranas and permeates it. The vijnanamayakosa is still finer and permeates the manomayakosa. Finest is the anandamayakosa. I don’t know what you mean by ‘astral body’. This is not a Hindu term. The causal body I referred to previously to above.
You wrote:
Can Spiritual enlightened person see Karana sharira (Causal body) and Sukshma sarira (Subtle body) of ours with his/her naked eyes or with Divya dhristi?
Answer:
A spiritually enlightened person may see the Causal Body as Maya. Some highly enlightened persons can see their subtle bodies with their physical eyes.
You wrote:
Can we see our own Karana sharira (Causal body) and Sukshma sarira (Subtle body) through meditation?
Answer:
As answered in other parts of this question, there is no individual causal body. You can see your own subtle body. Ramakrishna Paramahamsa describes this in The Gospel of Sri Ramakrishna.
You wrote:
Why does the Life span of each of the bodies is different in different people?
Answer: Karma.
You wrote:
Why does Sukshma sharira (Subtle body) called as Linga Sharira?
Answer: They refer to two slightly different things. The Linga Shariras consist of seventeen component parts; the five organs of perception, the intellect, the mind, the five organs of action, and the five vital forces (Vedantasara 61-64.). These make up the parts of the three sheaths that compose the Sukshma Sharira (subtle body). The subtle body consists of three parts - the vijnanamayakosa, the manomayakosa, and the pranamayakosa. The vijnanamayakosa consists of the intellect (buddhi) and the five organs of perception. The manomayakosa consists of the mind (manas) and the organs of perception. The pranamayakosa consists of the five vital forces and the five organs of action. (Atmabodha and Vedantasara).
You wrote:
Can living beings other than human also consist of these 3 Bodies?
Answer: Yes. The Chhandogya Upanishad (V.x.5-6.) says yes. In these verses are outlined the jiva’s path to rebirth on earth. After falling as rainwater the jiva is born as rice, barley, plants, trees, etc. Then - “…whosoever [capable of begetting children] eats that food and injects semen, they become like him.” - What the verse is saying is that if a male cow eats the plant, you are born as a cow. If a human eats the plant you are born human. Now, plants and animals (especially plants) have a limited or non-existent physical brain. So, you do not have the same ‘awareness’ of the physical plane as you do as a human. Plant life is more akin to a dream world.
I think there needs to be clarification on two other points you write. You wrote:
Man must take birth again and again with the help of gross body till all the Samskaras are consumed. You can consume Samskara (karma-phala) only in human life with the help of conscious living and power of will. It is not possible in any other life and that is why human life is considered as extremely important from the liberation point of view.
Not exactly. First, you take birth until you achieve Liberation. When you achieve Liberation, the only karma remaining is the karma of the present birth, the prarabdha karma, the karma that has already started to bear fruit. The accumulated karma still remaining, the sanchita karma, is destroyed, not consumed. Second, human life is the only life where NEW karma is made - not consumed. You can consume prior karma in other than human lives. For example, if you have very good karma, you can go to one of the heavens until the good karma that got you there is consumed.
