I'm think I'm starting to answer my own question here.  X-H1 will be the same as X-T2. XT-3 and XT-4 have the same sensors but not sure about the processors.  Would make sense to go for the 4 due to same battery as the X-H2.

Very backwards (haha sorry couldn't resist).

Nope - forwards only

Hi Guy, I need a secondary Fuji X to back-up my X-H2 cheeply.   I sold my X-T2 to get the X-H2 beause I wanted to increase my AF hit rate. That being said, can you comment on the hit rates between X-H1, X-T3, and X-T4 in 2024? With all having the latest firmware, is there a big jump in AF performace between the three? Thanks, Tomek  

oh wow, that is very odd.  Can you not simply put any version you want onto a formated SD card, and install it like every other priece of hardware on the planet?   @botty have you tried a different lens, or updating the firmware on your lens (if thats the only one you have one)?