MNO=Mobile Network Operator
Most countries only have a small number (3 or so) of distinct mobile networks.
MVNO=Mobile Virtual Network Operator
Any number of other companies can be a mobile network company by buying wholesale access to an MNO’s network i.e. reselling it
In other words … who’s ya SIM from?
APN=Access Point Name
A given mobile network may offer more than one service, differing in the level of service, functionality, … etc. offered to the connecting mobile client device. The APN selects that service. In many cases, the plan that you are on with your mobile provider implies what the APN should be (but connecting with the wrong APN may or may not work anyway and may or may not have negative consequences).
Linux comes pre-installed with a global list of all known MNOs/MVNOs and the valid APNs for each provider. However that list is not fully up to date.
If you mentioned that info here then someone could chime in as to whether your provider is working for that person in that country.
One successful connection to WiFi can cause a computer to notice that its clock is out of whack relative to the correct time and it can then deliberately drift its clock in order to synchronize (rather than just suddenly jumping by 9 months or whatever). In other words, drift can be a good thing.