Password Synchronisation


I'm trying to understand and validate some informations, we have a one way Migration / synchronization from domain source to domain target, my Questions:

- How does the password synch works ? it's based on the chage timestamp ? if I change the source Password does it replicate on the target with a full synch

- is there a way to fix the password copy Synch problems related to the doamin password policies (complexity, length).. the problem occurs when the policy is not the same on the target

-Where can I find the accounts who failed the password complexity

Thank you