Minecraft PE on the iPad. Multiplayer without the same Wi-Fi without other software?

My sister just called and asked if it is somehow possible that my nephew can play multiplayer with a school colleague on the iPad without both being on the same Wi-Fi network? Can this only be done with the game's on-board resources, or do I have to create a server for them?

Both must have a Microsoft account and you can already play with each other via the gamertag (i.e. The name)

So if they both have an account, can one of them join the other's map?

Yes, but you must have added yourself as friends, ie add friends to the right of the "Worlds" menu and enter the other person's name there

Yes, but you have to send a friend request