I would like to know whether we can have Two Servers with same Hostname in different AWS Region registered to Suse with same OS Versions or Different.
I never tested it but the most obvious is that the last hostname to register is the one that will stay with the active license.
You may try it and after it for SLE 12 or SLE 15 based clients run the following commands as 'root' user :
Common sense tells us that there should not be two systems with the same name exposed on the same subnet or on different subnets as long as they are interconnected. The same applies to DNS Name, there should not exist two IPs with the same name.