While Minecraft Java Edition is a premium game that requires a one-time purchase, you can officially download the Minecraft Free Trial to test version 1.12.2 before buying the full version. This specific version, released on September 18, 2017, is legendary in the community as the most modded version of the game, with over 46,000 available mods. How to Download and Install Minecraft 1.12.2
While TLauncher made the game accessible to millions who couldn't pay, it exists in a legal gray area. It violates the Minecraft EULA (End User License Agreement). While it is the "standard" way people play for free, it has always been criticized for stealing session data and showing intrusive ads.
Here are the system requirements for running Minecraft 1.12.2 Java Edition: