Let me first clarify point 2 of yours.
O-CSI is used for MO-triggers from the VLR. So if A makes call to B A’s MSC/SSF uses O-CSI to decide whom to send the DP.This O-CSI is obtained during LU.
B’s GMSC first fires an SRI(routing info) to get the T-CSI.
This T-CSI is then used to fire MT-Dp’s.
I could not figure out your 1st question though. Could you please elaborate on it?