Okay so the KND gang are probably all 16, so my basic timeline for the KND in RH is:
1) End of KND’s cartoon canon with Operation INTERVIEWS. Most of the real life interview sections however, are fake to throw off Father (or the GKND??) from Numbuhs 1 through 5′s true whereabouts. The content of some of the interviews however is canon. Like Numbuh 5 being/having been supreme leader.
Nigel is still offworld with the GKND.
Sector V are anywhere from 10 to 13, and Chad Dickson is 13 to 16.
2) The team is 13 and Chad is 16. Abby is supreme to a KND under attack. Lizzie Devine is revealed to be an alien in disguise, as well as a GKND agent codenamed Numbuh Vine. Nigel returns with an armada of GKND ships in tow, intending to wipe his home planet of anyone older than 12. Chad Dickson is captured by the GKND, and pleads with Numbuh 1 to go against his orders, and not wipe the planet of all non kids.
3) Things happen, and the day is saved. All we can confirm is Nigel eventually rejoins the good guys, and the world as they know it doesn’t end. Eventually Numbuh 5 retires from the position of supreme leader via tag or appointing a successor. 1 and 5 return to commanding Sector V either together or in their original 1st and 2nd in command configuration.
Notably no one is decommisioned. It’s possible decom has been made optional or reserved for retirement. More likely however, all of Sector V proved themselves deserving as TND operatives in saving the world from the GKND.
4) The kids start attending highschool, probably Hendry Middle, for at most 2 years. Numbuhs 1 through 5 are now 16, and Chad is 19.
5) Reaper High begins(appears?) and all of Sector V begin attending as Juniors during year 1. Who the heck knows what Chad is doing here, probs just checking in on Sector V because he is still protective. Go to college Chad, your mother is crying. If she even is your real mom, honestly I wouldn’t be surprised if that shit was fake too at this point.