As per delay in detonation - it was introduced in later missiles (M/M2, probably), to counter early detonations due ground proximity (that's what I found in I-net)...
Nop.This is not truth.
The delay detonation is huge improvement of OSA system, for engaging helicopters and receding targets.
The ground effect possible detonation and thus the OSA missile not to go lower than 25 m was solved to OSA akm model ,introducing new trajectory of missile higher from the line sight of TTR (zoom climb mode-part of method Fi).
