vowel shifts in mordern indian

[Rajarshi Banerjee]

Here is a snippet form a thread in another group.I was wondering if someone
with knowledge of comparitive indian grmmars can throw light on some of the
questions

GJ>It is just that the evidence for e/o is only indirect *as I said, it
substist before velars, because velar before the front vowels e palatalise).
RB>Just want to clear something. does the front vowel e change the preceding
stop or the following stop. In gneral, I can see either happening.
so does kek -> chek or kech or chech. I am thinking also of loch in scottish
and ich in german.
1) Historically is the final stop ever influenced by the preceding vowel.
In indian vernaculars we see even dentals changing to palatals satya->sach
(hindi) sachcha(spoken telugu) (fronting in ya colours the preceding
dental?). Whereas in bengali satya -> shotto retains a dental because of the
back vowels.
2) Ablaut,e/o reflexes could be detectable due to palatalization. Is this
indeed the case in sanskrit when it comes to grammatical variation on the
root.
3) Bengali is the only language I know which has undergone a backing of
vowels rather than fronting, are there other cases like this?
regards

RB