I bought Minecraft from Mojang years ago. Now I have a Microsoft Surface and would like to play Minecraft there too. Do I have to buy Minecraft again in the Microsoft Store or is there a way to transfer my account at Mojang?
You can log in to the Mojang site with your account and then click on "Get a free Copy" or something, then you will receive an activation code for the Microsoft Minecraft
You have to buy it in the Microsoft Store as far as I know
You can also just play the normal Java version on the Surface.
Not if she bought the original years ago - back then you got a key for the Windows Edition.
You still get one.
As far as I don't know, at least from 2018 onwards you couldn't get any more when you bought the Java Edition.
I think the reason is that a lot of people with alts just got a win10 key.