Below document covers details for browsers, os versions and jdk versions for ebs 11i.
Recommended Browsers for Oracle E-Business Suite 11i (Doc ID 285218.1)
while below will cover details for browsers, os versions and jdk/jre versions for ebs r12.1 and r12.2
R12: Recommended Browsers for Oracle E-Business Suite (Doc ID 389422.1)
I believe you will have to get a common version for os platform, web browser, jdk/jre version from above documents to make sure 11i, r12 and r12.2 work seamlessly.
What's the error you get when you open the forms from 11i?
IS it 220.127.116.11 ? There was one issue in opening forms for 11i. You need to copy jvm.dll
We also have 10g forms custom application which runs on Jinitiator. We installed both Jinitiator and JRE and it works.
Mohammed Ali A. Syed