Hi Arun,
There is no such mandate that you have to go to CF 9.0.2. As ColdFusion 9.0.2 update is a summation of ColdFusion 9.0.1, ColdFusion 9.0.1 Cumulative HotFixes 1 & 2, all ColdFusion 9.0.1 Security HotFixes,without verity so you are getting the same security updates in 9.0.2 which are there in 9.0.1 but without verity however there is an updated JVM
You can check the changes mentioned in the CF 9.0.2 release notes : http://helpx.adobe.com/coldfusion/release-note/coldfusion-9-0-update-2 .html
There was a hotfix release for CF 9.0.2 which you cna check here : http://helpx.adobe.com/coldfusion/kb/cumulative-hotfix-1-coldfusion-90 2.html
The latest update for CF 9.0.1 is http://helpx.adobe.com/coldfusion/kb/coldfusion-security-hotfix-apsb13 -27.html
Check this article as well : http://www.carehart.org/blog/client/index.cfm/2013/8/19/understanding_ ColdFusion_9.0.2_a_FAQ You will find this article much helpful
HTH
Thanks
VJ