We have never applied any of the CPU patches to our system, currently we are on 18.104.22.168.
From which year i need to start applying the patches,please advice..
and i also if we upgrade to R12, did all CPU patches from 2005 included in R12 patchset?
I would open an SR and get Oracle's advice - if you have been running since 2005 with no CPU patches, there are a ton of them, many have been superceded, etc. and it will be a lengthy process to research each patch, whether it has prerequisits, been superceded, etc. Starting this year they are cumulative, but you'd still need to patch yourself as far as end of 2010 before starting on the cumulative patches.
Also ask them about the 12 upgrade with regard to CPUs.