That is most definitely wrong! It should be 'in which your boots are'

• My coat is in the wardrobe, in which your boots are.

This is a quite awkward and unnatural translation into English (at least for a number of us). It may be formally correct, but nobody I know speaks like this.

A more natural translation:

• My coat is in the cupboard which your boots are in

Note the change of word order.

My answer was marked as incorrect because I used this word order.

Please don't correct my English duo - it is my native tongue - I want to speak Hungarian better!

"your boots are in" is the less formal way in which we speak English.

Everything is okay with :"In which is are your boots"?

Why not ' my coat is in THAT wardrobe....?