The VIN system is different depending on the market.
Acura (LHD/RHD), European models, JDM all use different system so you can't decode it using different system.

The NSX you mentioned is called NA1-100type, 91/92 model, left the factory with the 1st gen. ABS.

Year model depends on the market as well so be careful.
In any case, NA1-100 is the original spec.

In Japan, there are several organisations that can check the history of the car.
Seems like your friend doesn't have any documents but you may be able to ask Honda dealer to check the previous service history.
If there are any service receipts with lots of parts no., then that will help in understanding what was changed in the past.

You can contact JAAI, Honda dealer, car auction members, etc for other checkups.

Kaz