I flew HKG-NRT on ANA a few weeks ago. NH812. Great service. I've flown this many times.

I was able to check in enough via ANA to change my seat but that's all. Make sure you use the international tab on the website; it defaults to domestic. The process would not fully complete. ANA check in agents use UA app to determine luggage eligibility but then also reference NH rules for Star Gold. They don't know how to apply the rules well.

Definitely reprint BPs in NRT to get precheck and boarding group on your BP. (NH may show group in small print as zone but I'm not sure all match up exactly.)