Verified answer

1) Have they sent us any telegrams lately?

 Have we been sent any telegrams (by them) lately?

2) She said that they would warn her about it.

   She said that she would be warned about it (by them).

3) Are you still interviewing this student?

  Is this student still being interviewed by you?

4) They have demonstrated that film many times.​

   That film has been demonstrated many times.​