Core Fighters includes four playable characters: Ryu Hayabusa, Hayate, Kasumi, and Ayane. Opponents span the same roster as the full version, and all stages are included. Tutorial and training modes make the F2P version as well, but the story mode does not. In terms of in-game purchases, additional characters cost $4, while the story mode is $15.
As for online play, it's enabled for free, and players using the F2P and retail versions of Ultimate can fight each other. However, neither version of Ultimate is compatible for online tussles against players using the original Dead or Alive 5, or Dead or Alive 5 Plus on Vita.