The account feature in DragonBox Numbers will allow for game syncing in the future. This is currently under development.
However, if you change your profile name to WWTK in DragonBox Numbers, all the levels will be unlocked for you. You will also receive a large sum of coins, which will allow your child to go back and play previous levels.
For DragonBox Algebra 5+, DragonBox Algebra 12+, and DragonBox Elements, there is a way to unlock all the levels of the game. Name your profile to ALLOPEN, and you will be able to start wherever you want in the game.