Hello,
I have a question, can I downgrade license from SUSE 15 to SUSE 12?, or I need to buy another license for SUSE 12, this is because I bought a server with SUSE 15 but I need SUSE 12 because all my applications is working with this distribution, Thanks.
@“Daniel Oscar” Hi and welcome to the Forum 
Yes, just download the install media for SLE 12 and install and register, the license is valid for any release still in General Support to receive updates etc.