1.What is interesting is that Sanskrit and Prakrit are treated as mutually intelligible is a good starting point. But one could argue that in an environment of bilingualism or multilingualism too , two different languages can be mutually intelligible.
2. Filtering the value-terms such as correct , incorrect, refined (samskrita), corrupt (apabhrashTa) etc., it can be seen that Sanskrit and the Prakrits were considered always alternative forms of each other. Whether Samskrita is considered to have been formed through the samskaraNa= refinement of prAkrita or prAkrita is considered to have been formed through the apabhrams'a = corrupted form of samskrita , the point is that in both the perspectives samskrita and prAkrita are considered to have been formed through the modification of either one from the other.
3. The classical drama's presentation of the two as the social class based mutually intelligible versions of the same language too matches with the above mentioned view under no.2.
Thanks to all the colleagues on the list for the references. I shall take the help of all the books.
Thanks again.
Nagaraj