I have upgraded magento to 184.108.40.206, i wanted to confirm will it also install all patches including SUPEE-6788 by default..? or we have to install SUPEE-6788 seperately in magento 220.127.116.11 ?
Yes, Magento 18.104.22.168. includes the SUPEE-6788 patch bundle. If you upgraded to Magento 22.214.171.124 your installation is fine so far.
See also the official resources for some more information:
SUPEE-6788 Patch Bundle
This patch bundle protects your Magento installation against several potential threats, and includes a new configuration setting that helps manage the backward compatibility of the patch for extensions and customizations. The first patch in the bundle was included in the Magento Community 126.96.36.199 release. However, versions of Magento Community prior to 188.8.131.52 need this critical patch.
Admin routing compatibility mode for extensions- did your upgrade went well? Have you cleared the cache? What does the current version says in the back end footer?