You can do this in Offline > Practice mode with any characters. (Following example uses Heihachi)
Take a look at the info panel on the stage select screen - you'll be able to see the location of breakable balconies / walls / floors on each different level of a stage.
I haven't found a definitive answer to what allows for a floor break - but a reliable approach is to spike down an airborne opponent. So start a juggle, then slam them down with a "bound / tailspin" type move.
Example: Heihachi's Demon Uppercut (
) followed by Jichinsai (
The Forgotten Realm stage has 4 levels. You'll have to break through the top 3 floors (anywhere should work) to unlock this achievement.