1.) Do you mean location wise, or how they came to be? 2.) Halsey was in a multitude of places. During Halo CE, she was hunkered down in CASTLE base on Reach. After being rescued by the Master Chief, she would kidnap Kelly and leave the group she was a part of behind. During Halo 2 and 3 is when the events of Ghosts of Onyx and sections of Glasslands take place. She eventually made her way to Onyx, and she and Mendez, along with a group of Spartans, took refuge in Shield 0006. After that, the group was retrieved from Shield 0006, and Halsey was taken into ONI custody. Once thoroughly debriefed by Parangosky, she was sent to work on the UNSC Infinity with Dr. Glassman, and eventually ONIRF Ivanoff. 3.) Yes. Depending on the candidate, the start age was 4 - 9.