This is a random variant, which appears randomly in the world. Random variants change upon reloading the world.
You know that you are generally NOT allowed to:
But you also know that you are allowed to:
In general, you should pick your current Minecraft version, which you are playing with. Then the pack will definitely be compatible with your game. In case your Minecraft version is not listed here, you should pick the most recent one that is listed.
To find out, which version you are using you need to open up Minecraft and look at the title screen. In the bottom left corner, you will find the version number. You only need to look at the first part of the number. For example in this image, you can see Minecraft 1.16.
While every version of Minecraft is still Minecraft, the differences between the Bedrock and Java versions can be quite extensive. To answer the question of which version you are using, you will need to open up Minecraft and look at the title screen. Then you will see the following difference.