this post is questionnaire more than a technical, EBS startCD 51 released before 1 month and it's comes with different features such as DB 12c will be installed and it's support RAC installation Features immediately which mean you don't have to install EBS on Single node then convert to RAC.
Like the above pic, well everything done successfully for DB installation without any problem same as below :-
The installation is multi - node which mean Apps on different server, when trying to connect APPS to RAC DB each time the same error appered with no sense which is
ORA-12514: TNS:listener does not currently know of service requested in connect descriptor
Be noted that the DB is reigster with SCAN and tnsping is working , and i can access DB using TOAD thru SCAN or Local Listener
Therefore after multi try of the installation and fix the error, i choose the old way which is Single node and covert to RAC and the funny thing it's working without any issue.
If there is any idea about this error please comment below maybe i missed something