i upgraded the 10g(10204) RDBMS of R12(1206) to 18.104.22.168 using
Interoperability Notes Oracle EBS R12 with Oracle Database 11gR2 (22.214.171.124) [ID 1265232.1].
In the post install steps, It says to run catmgdidcode.sql , but I cannot find this script anywhere
But I see no value in doing what you did. 126.96.36.199 was an initial release and will require substantial patching. My recommendation would be to go directly to 188.8.131.52. But best practice would be to discuss this with Oracle Support and get them involved.