Each game has 44 Ranks except Papa's Hot Doggeria, which has 59 ranks. Once you reach Rank 44, (Which is the "Better Than Papa!" rank) there will be no more ranks even if you pass the number of points to go to the next rank.
Nothing is unlocked at rank 100 (everything is already unlocked). A lot of characters are gold, including all closers. I'm using the Health Nut special, which I consider the best special in the game. It's the last special you can unlock and gives 250% bonus xp.