1) Global variable names are disable right now. Hopefully, they will fix this in the next release. A real pain.
2) Copyright law (in the US) has to do with artwork. If you copy a Pac-Man or Donkey Kong graphic, then that is infringement. If you create your own picture, it is not. Trademark infringement has to do with trademarks or logos. So having a Apple with a bite out of it would be a trademark issue.
What you name stuff inside of the game is never seen so no one cares. Now, trademarks are by industry and I think there are like 12 of them. That means Mcdonalds may have a trademark for food but you could have one for clothes. The big companies will run the gambit and trademark for every industry,
Still, can you call your game Pac-Man?
If Namco has a (r) or TM, then they have laid claim to that name or registered it. But did the guy who did Flappy Birds get a trademark on the name? I don't think so. You could have a game called Flappy Birds.
Basically, you're OK.