1. How to cleanup test instance [remove EBS , DB ,making room for fresh copy of prod]
Follow this document if you don't have any other Oracle product on the server:
11i: How To Clean Up The UNIX Environment After EBS 11i Install Fails (Doc ID 110372.1)
2. How to clone EBS apps and db tier ? [in which sequence these task will complete]
Cloning Oracle Applications Release 12 with Rapid Clone (Doc ID 406982.1)
3. What about IP and host names?
When you run adcfgclone as part of the cloning procedure, you can specify the host name that will be used to run the instance.
Of course you must change the host name and IP address before you start the cloning process.