So the K3 command (when in RABOTA PO K3) is sent at the exact time regardless of DOGON mode. The actual delay is provided in the warhead timer (and set before flight, when the missile is on launcher), right?

At the Volhov, you have these methods...
ZEMLJA - ground - detonate missile by command
STAN - arm the fuse 300m before the range boresight - detonate by radio proxy fuse
RAB PO ADA - against spy balloons - detonate missile by command, well before the target
ZAGRUB RV - reduce fuse sensitivity to avoid detonation by chaff
ZAGRUB RV USU - reduce fuse sensitivity to avoid detonation by chaff with USU missiles
NLC USU - gate fuse sensitivity to 100m against low flying targets
NC USU - used with nuclear missiles
RAB OT VM - arm the fuse 11sec after launch - detonate by radio proxy fuse
RAB PO K3 - detonate missile by K3 command

At the Dvina, you have these methods...
ZEMLJA - ground - detonate missile by command
RAB PO ADA - against spy balloons - detonate missile by command, well before the target
11 SEC - arm the fuse 11sec after launch - detonate by radio proxy fuse
RAB OT RV - arm the fuse 300m before the range boresight - detonate by radio proxy fuse
RAB PO K3 - detonate missile by K3 command for incoming targets - used against low flying targets
DOGON - detonate missile by K3 command for receding targets (Dvina has no K4 command to transmit the missile/target closure speed)