When making online payments, where it asks to fill in the billing address, should I use the billing address of the underlying card? I have cards from more than two countries, does that mean the billing address for my curve card is changing depending on which underlying card I am using? Can I go back in time for a card with different billing address when making online payments?
In my opinion you should enter the address of your Curve account.
The webshop does not know which underlying card you are using, the webshop only sees you are using your Curve card (with associated address).
So also going back in time with cards that have different addresses should not be an issue.
I always entered my real address
Yes, use the billing address that Curve have for you