"You cannot advertise an ibgp network to another ibgp peer"
Are you sure?
AS-Path change only when update send to EBGP peer, so loop detection based on AS=path don't work in IBGP session.
Best regards. Alexey Nesterkin
Good day.
Multihop not used for IBGP.
Sometimes session established if on other side was configured update-source Loopback0.
Best regards. Alexey Nesterkin