How do I stop a looping command block in Minecraft for Windows 10?

This morning my sons apparently made a command block today that pumps out wolves to the point they've crashed their game and it now locks up within a second of restarting it. I assume dying under the weight of too many entities. I asked if they had time to type in a command like /kill all entities to then give them a moment to move to and destroy the block and they said no.

In the Java version I'd be able to do things like open and edit the world offline. With the non-Java version though I'm stumped. How do I stop this looping command block?

There is a tool called Universal Minecraft Editor which is capable of reading and modifying chunk data of a world. You can download it here: https://www.universalminecrafteditor.com

when you open it, it will ask you to choose a platform so choose Win10 (not sure if Bedrock edition is considered Win10 or Pocket Edition so experiment with that).

The next screen will allow you to choose a save file so do that and click open. Once the save is open, click on "chunk locator" button on the sidebar and find the area with the command block. Click on the chunk which contains the command block and click "open". A new window will pop up with with a hierarchy view and a branch called Level or something simillar. Expand the level branch, expand "Tile Entities" and you should now see all the tile entities including the command block itself. Simply remove the command by double-clicking on the command field.

The same goes for the entities. Click on the chunk with the entities, click open, expand Level, expand entities and delete them.

Once you're done, click the three dots on the top right and click save all.

If you don't know how to do it, I'd be happy to help with that. Good luck!