Downgrade from HDP 2.6.5 to 2.6.0.3

[#1]

I need to downgrade to hdp 2.6.0 from 2.6.5, I am able to register it but not able to install.

[#2]

Unfortunately there is no way to downgrade.

Best will be to uninstall HDP 2.6.5

https://community.hortonworks.com/articles/97489/completely-uninstall-hdp-and-ambari.html

And install HDP 2.6.0.3

Take backup of critical files on HDFS and configuration databases.