The WordPress Support Forum and WordPress Codex only provide support and documentation for officially released versions of WordPress, as downloaded from https://wordpress.org/download/ and only from https://wordpress.org/download/.
The only current officially supported version is WordPress 4.7.1. Previous major releases from 3.7 onwards may or may not get security updates as serious exploits are discovered.
If you are unable or unwilling to file bug reports, and help fix problems, please do not use anything other than the officially released versions.
WordPress will be backported security updates when possible, but there are no guarantee and no timeframe for older releases. There are no fixed period of support nor Long Term Support (LTS) version such as Ubuntu's. None of these are safe to use, except the latest series, which is actively maintained.
For the list of WordPress Versions, refer WordPress_Versions.