2 objects

Is that you, Antonia?

This is nothing but  a try...

If I had to make a passive sentence I could only make one sentence:1) My key was returned to me. Couldn't I? It isn't possible to put the indirect object (in this case) in the beginning of the sentence, like: I was returned my key.Of course in some cases it is possible, but I believe that from these active sentences only one passive sentence can be made.

The same question goes with sentences like:

2) They didn't allow us to take them home. (We were not allowed to take them home, but They were not allowed to be taken home with us sounds awkard.)

3)People will show the visitors the new buildings. (Is it possible to say Visitors will be shown new buildings.?) Yes, but "the" new buildings

4) Somebody recommended me another doctor. (I was recommended another doctor?) OK

5) Someone taught him French and gave him a dictionary. (He was taught French and given a dictionary. Is there any  possibility to make a passive sentence beginning with French was taught and a dictionary given to him?) sounds dubious

6) Someone will read you another chapter next time. (Another chapter will be read, but not You will be read another chapter.) no, it's OK

I really can't help you with your question   

I'm no grammarian, so you'd better wait for someone else. Mathematically I think you can make any passive sentence, but the thing is to see if they're used... For example, I wouldn't use "I was returned my key", I'd use "the key was returned to me", but I can't explain why ...

Let's wait...