World Rank

Normally, as you progress through the game, you notice that the Pokémon you face and collect start going up in strength levels through the natural difficulty progression. However, what this causes is a vast amount of Pokémon being stuck at lower strengths, unable to face up against the opponents in the later parts of the game which occurred in the original game.

However, in Pokémon Rumble Blast, after you have completed the main storyline, you gain access to the World Axle Upper Levels which has a special where you can rank up all the Pokémon in the world. This will change every Pokémon in every to be of similar strength levels, evening out the playing field so Pokémon of all species can fight in the final battles. To get the various ranks however, you need to pay and the price is high.

Legacy Mode

Once World Rank has been activated, there is a way to revert all thes back to how they are meant to be. This is done via "Legacy Mode". This mode is accessed when you load up the game. If you hold L and R down while holding Left on the Circle Pad on the Title Screen when you start the gaming. Now, when you go into thes, the Pokémon's moves and levels will be the way they were when you first entered them in your gameplay. This allows you to collect low levelled toys to exchange for moves in Axle Town and gain Pokémon for evolution. However, Pokémon that only appear in thes after the end of the game shall still appear.
This mode can be reset by returning to the title screen