Introduction: How to Play Different Versions in Minecraft Java Edition.
Let's say one day you're looking at some really cool Minecraft maps and then, oh no the map is for 1.12 only and the Minecraft launcher only has the latest release and latest snapshot. Today is your day because I will teach you how to get different Minecraft installations or versions. Note: In the latest Minecraft launcher version you will have to check a box if you want to play a modded version.
This is for Java Minecraft only
Step 1: Getting to the Installations Tab.
I already have some different versions in stalled so I'll try to always put a box around what to do.
The first step is to open the Minecraft launcher and then click on the installations tab.
Step 2: Navigating the Installations Tab.
The installation tab has two main parts, the search bar and filters (outlined in red) and installation list (outlined in blue).
Step 3: Making a New Installation.
This will be a long step so buckle in. As in the first picture click the new button and you should see something like the second picture. Once you have clicked the new button the menu that pops up has a few different settings I marked the most important ones but will go over them all. The box marked "1." is the name box you can name it whatever you want I usually leave that blank but it is up to you what you name it. above the name box is the installation picture, you can set it to whatever you want once again I leave that alone but it's up to you. the box marked "2." is the version box this will affect the version you download so scroll until you find the version you want. Once you have everything to your liking just hit the create button shown in the third picture and then the installation is ready to be played. (After you click play there will be a download bar and then the game will start.)
Step 4: Extra Info
This method will also work for snapshots and historical releases all you have to do is check the box in the installations tab.
WARNING: Loading a world into an older version than it is currently running could cause the file to become corrupted so change versions at your own risk. That being said updating the world to a newer version is less dangerous since all the blocks from the previous version are in the game.