When I was getting ready for my cruise last month, I also had to get a tech on the phone to get my name "validated" and my passport entered..
Once he got that all fixed, everything else followed pretty fast. He also told me that once the information was in the app it would stay.
The day I got off the ship (Mar 30th) the app said "off ship" but all my info stayed on.
I booked a cruise a week after returning for next March.
Currently, my app has a count down clock and most of my info is still there. Personal info, passenger documents, travel documents, profile photo, security photo, emergency contact all have a green check
I have to enter my charge card or method of payment, travel information, health status, link bookings and choose your Medallion wearable. Closer to the cruise.
So I would have to say that as soon as one cruise is finished the next one pops up with all the info and you just have to add current info.
Regarding a b2b..My cruises had only one booking number ..so one medallion for both legs of trip..but I did get two mini bars.