on which platform onwards weblogic introduced in EBS and why and what advantages or replacing Apache server
WebLogic Server is included in release 12.2 on the application on the following platforms:
IBM AIX on POWER Systems (64-bit)
Microsoft Windows x64
Oracle Solaris on SPARC (64-bit)
You can check the certifications tab on MOS for exact details on which versions of each OS is certified.
Here is a link to address your second question: