Questions about devil,after life and cast system

Question: whether, really, devils exists, or it is simply,our imagination?
when we know that, after leaving one body, it will gain another, then why do the necessary to perform VAIDIKA KARMAS?

Both the above questions are interlinked.
I dont know whether you heard my talk on pranayama where in i talk about the Udaana vayu. I dont go into details here but I explain there at length that Udaana is not only connected with this body but it acs as a brodge between ths body and transcends. That Udaana is the store house of our memory. it is beyond this body. even when body is not there Udaana suvives and the immediate body impressions are carried by this udaana for few days after death and our soul will have this udaana attached to it and will stay in this area our body used to be there. that is why some people have seen that a person is still living in the same place for some more time after death and is experienced like participating in the conversations after death. strangly this is for thirteen days therfore we have thirteenday ceremony after death.
Even after that the Udaana carries the impressions of the ambitions of the person. Inorder to convert these ambitions into reality the person will not have a instrument called body So such intentions will try to associate with one who has similer intentions and persuing. Thus we see when ever we are doing any work we suddenly feel some extra energy is working and with our energy we would not have achieved it. This applies both for good work and bad work. This is what in Gita Krishna says 'Devan bhavayataneva te deva bhavayantavah' But two thins we need to understand such forces help us in our persuite. but intention in the first place is ours and secondly we are stronger and we have the advantage because we have body, they dont have one. They can never be stronger than us. These forces people call a ghosts or devils. Therfore devils are Udaana mounted soul or consciousness which has left the body and waiting for a suitable new birth to persue the ambitions!
People do the Karmas during the initital thirteen days becasue that is the period when the person is aaround the same surroundings hoping to interact and the living people by doign these karmas will make them feel satisfied and cared so that the departed soul will have peace.

Question: When actually,this present ,cast system came to exist/and why it came to exist?

Here Caste system was always there and will always be in some for or the other. What our people have done even in hte times of vedas is to give a proper shape to it. But some how in the middle times it has been abused for personal gains so it went into wrong hands. I have written in one of my articles about the importance of the caste system. One thing is that we need to resturcture the system after understanding its importance and What is happening now is people do not understand but meddle with it fo rpolitical gains or people discard it without understanding it like throwing baby with bath water.

Love,
Raghuram.