CBS executives, upon viewing it, realized that the character of Chin Ho had been killed off at the end of the 10th season of the original show.
The project was overseen by Steven J. Cannell who, apparently, hadn't viewed the episode where Chin Ho was killed off.
Yes. The roster of Five-O vets included James MacArthur as Dan Williams, now the governor, Zulu and Herman Wedemeyer. Gov. Williams is shot and the new Five-O teams up with retired Five-O members to try to solve the case.