Ответ:

What have his friends done recently?

Who have his friends sold a new cottage to recently?

What have his friends sold to the neighbours recently?

Have his friends recently sold a new cottage to the neighbours?

Who did his friends sell a new cottage to in the country recently?

What did his friends sell recently to the neighbours in the country?

When did his friends sell a new cottage to the neighbours in the country?

Where did his friends sell a new cottage to the neighbours recently?

Whose friends have sold a new cottage to the neighbours in the country recently?