I would like to set the spawn probability of the ores really high in Minecraft, but I couldn't find any mods for 1.12.2. How do I increase the probability that I would play all versions from 1.12.2.
You can do that in the Vanilla Worldgenerator.
Simply go to "Create new world" on "Go to more world options" and there under "World type" go to "Customized" and click on Next there until you get to the spawn opportunities. (Tip: you can also adjust the spawn height there)
Great, thanks, which version does that work?
I personally tested it in 1.8. From there you can do this in any version (this may also work in 1.7.10, but I don't know)
Until 1.12
But again from the 20w21a (aka 1.16)