I have intelliJ 12 30day free software installed with entire project setup and running ; now I have a license received from my company and it is not allowing to register; then realised it is a license of intelliJ 11 version; please lemme know steps to downgrade to intelliJ 11. Like running a patch or what is the solution?
Download and install the old version from this page.
Another option is to use the JetBrains Toolbox App. It allows to install multiple IDE versions, perform rollbacks if needed, applies updates to the IDE and plug-ins, etc.