Downgrade Minecraft?

I was pretty sure I’m supposed to just open the Minecraft launcher, go to installations, new, then change the version to Minecraft 1.12.2 from the drop down list but the list only shows versions 1.13.2 – 1.14.4 for some reason.

I have the historical setting ticked and i haven’t been able to find anything helpful so far. Sorry if this has been solved before in another post/many posts, but I’ve just spent the past ~hour of my life trying to figure this out and I just can’t find it.

Did Mojang actually removed old versions of Minecraft? If so is there any way to get them back? New versions are really too laggy for me.