Answer:
Nominal; Yes, it changes to ordinal.
Step-by-step explanation:
1. Nominal: Since "ISBN group identifiers" consists of only one in number per country, one cannot rank each and every identifier as better than the other identifier or that there's additional of them, because this is just a group identifier, and hence not a group measure or count. Usually, there's only one in number per country.
2. Yes, the level of measurement changes to ordinal : As per assigning a higher level of group identifiers to higher population countries, one is adding the other category of data whose role is to organize and order country with respect to the population. Henceforth, numerical ranking and categorical processes are included.