Re: 3 Registries for the Yamato?
As long as it's not an obvious joke (like the duck and hamster-on-wheel in the Ent-D's engineering schematic), I view the registry number as given on onscreen readouts as no less "hard canon" than anything spoken in dialogue.
As we all know, even dialogue can be obviously wrong, such as the "200 years ago" line (regarding Khan) from DS9. So just because something is actually spoken doesn't mean it's untouchable and therefore always right. Dialogue is subject to the same scrutiny as anything else.
It is by caffeine alone I set my mind in motion. It is by the beans of Java that thoughts acquire speed, the hands acquire shakes, the shakes become a warning. It is by caffeine alone I set my mind in motion.