1.Jane doesn't know anything about the city although she has come there twice.

....Coming to the city twice, Jane doesn't know anything about it......................................................................................................

2,Because he didn't prepare the assignment,he didn't get good mark.

.....Not preparing the assignment, he didn't get good mark.....................................................................................................

3.After he had finished his work,he went out with some friends.

..........After having finished his work,he went out with some friends........................................................................................

4.Mary realizes that her dress is out of fashion after she has looked through the fashion magazine.

..............Mary realizes that her dress is out of fashion after  looking through the fashion magazine............................................................................................

5.Because he was exhausted by his work,he left the office earlier than usual.

........Being exhausted by his work,he left the office earlier than usual.

................................................................................................

6.The house was built of wood,so it was clearly a fire risk.

..........The house  built of wood was clearly a fire risk................................................................................................

7.She didn't know where th theater was,so she asked for directions at the hotel reception.

..........Not knowing where the theater was, she asked for directions at the hotel reception................................................................................................

The question which/that he has put forth is very difficult. I can't find an answer for it at once.