Yes, these versions are slightly different, especially when it comes to drawing things. Also, some variable names differ, too. Besides that, games made in v1.0 are much, much faster than those that were built in v0.5.2.
As you are a new ct.js user, I recommend you to start using new ct.js v1.0 from the alpha channel, as it is a fully usable product: it has its own separate docs and tutorials, examples adapted to the new version. I also migrate some of my games and haven't seen any issues.