What did the governor of Glubbdubdrib invite Gulliver for ? What did Gulliver wish for ? How did the governor a life him ?

The Governor told Gulliver that he could speak to any ghost he chose and to as many as he wanted. But Gulliver had to promise to ask them questions only about their time.
Gulliver wished to talk to Alexander the great, Hannibal and Roman emperor Julius Caesar. 
The third part of the question is not clear