How do I play on my Minecraft world?

Hey, I made a world on Minecraft PE and I used the newest version.

I wanted to use an older version to play on the same world but whenever I click on that world it says I can’t use it because it’s a different version.

I was wondering, how can I change the world setting or anything to be able to play in that world without updating my game, I want to play in an older version.