How to downgrade the client version for Java Players,
- Open the Minecraft Launcher
- Click Installations (located at the top tools bar)
- Click New Installation
- Enter a Name (optional)
- Select what version to make the installation (e.g 1.20.4)
- Click Install (located at bottom right of screen)
Locate the “Installations” Tab at the top of the screen.
See Increasing Your Ram for guidance on increasing the amount of RAM allocated to the installation.
Once on the Installation screen, click New Installation.
Enter a name if you wish, select the version of Minecraft and click Install.
Lastly select the new installation, and click play!