How can i make a minecraft version other?

I wanted to know how I can change from 1.12.0 to 1.14 in Minecraft.

As far as I know, this is not really possible in the singleplayer. The version with which you start the world remains. If you start minecraft with a newer version and then want to go into this world, a warning comes. Then you can update the world to the newer version. However, I believe that this can destroy the world and probably many new elements can't be adopted.

Can't confirm that is only my guess based on experience

You're welcome.

You start the launcher, go to installations, go to New and create a profile with the version you want. Now you go back to games. Below links you will find the profiles. Now you just choose your desired version and finished.