There is one separate recording session with 2Pac and the Outlawz, and a later recording session with only the Outlawz (this time featuring Kadafi). Just listen to Kadafi's verse on your copy of the song. Is there a very loud, reversed high-hat every bar or so? If it's there consistently throughout the track, Pac's verse was mixed in to the Outlawz version. If it's there only during Kadafi's verse, it's the opposite. I guess the info you should care for here though is that Kadafi's verse was not recorded in the same session as Pac's.
My guess is that the song was recorded not very long before Pac's death, and then re-recorded in the weeks before Kadafi was shot too.