I find this type of single line "new postings" asking details from the readers, then discussion drifting, digressing, deviatng to different topics.
Why can't the posting authors ask specifically theitr clarfication, doubt or interpretation, so that one can directly proceed from there.
Evidently, the question depends upon the title and pre-conceived and therefore, unless he comes out with eaxctaly what he wants to know about the so-called "old-Indic" and "Old-Iranic".
H. S. Spencer and others have dealt with elaborately.