[TYPO3-install] How to install 4.5.27 with same configuration of 4.6.1?

[Ilkcan Cakirli]

Hey guys,

I want to help a friend in a small company to reinstall his system but with a different TYPO3 version. He is currently using TYPO3 version 4.6.1 and has the following problem in the backend :
You can not log in to the backend with a newly created account. The error message is: "local langfile Could not be written to typo3temp/locallang-BE- ... "

I could not find a solution to this error message and since his version is not supported with new updates anymore, i suggested him to re-setup his system with version 4.5.27, and then upgrade after the release to version 6.2 with Easy Migration.

However, there are not any user manual or documentation to the configuration of his system. So, i have to understand all configuration by myself and document changes made to replicate his old system in 4.5, right?

So, how can I perform best? What should I back up , where do I copy, what I can leave out to accomplish this? Thanks in advance