Hi MGS,
For unchanged addresses, GTS only performs status check of Business Partner whereas if the Partner address is changed in the document, system performs rescreening (depending upon screening type and configuration) and gives the result.
GTS doesn't determine itself whether document address is changed rather this information is sent from ECC to GTS as I explained in my previous post.
Since, you are saying that the document is blocked everytime you change partner address manually in document, there can be two reasons:
1) You have setup asynchronous screening.(read thread for more details: scn.sap.com/thread/3876108)
2) You have setup "New check of changed addresses" in customizing. (read thread for more details: scn.sap.com/thread/3842075) - I am yet to verify this behaviour though.
To answer your other questions:
1) In either of the cases, unchanged address or manually changed address in a document, GTS considers same fields for screening as per SPRO customizing settings as per your first post.
So in nutshell, a manually changed address will go through rescreening in GTS whereas unchanged address will only have status check.
regards,
Kul Vaibhav