1) I'm not really understanding the problem here. If you have multiple Apple accounts then that turns into a management issue. Unless you really know how Apple accounts and iCloud work you can get information from one account mixing with that from another, particularly if you are using an Apple mobile device. Are you simply seeing data that you think is in one account on a second one? If that is happening then on a previous log-in to that account you may have selected to keep the data from the old account on your device.
As you can tell, I may be completely misunderstanding this issue and it would help if you could explain in a lot more detail what it is you are doing or even if I am right about two accounts being involved.
2) See the section titled, "What if I don’t recognize the location shown in my sign in notification?" by clicking on the link for this support article 'Two-factor authentication for Apple ID' --> https://support.apple.com/HT204915