It bothers me that neither of the other answers are quite right. As a native speaker and a teacher, I'll clarify properly... 1) "what is the family going to eat" is correct. "what will the family be eating" is another option. (the suggestion that "what is the family eating" can be used for the future isn't quite right as it implies they're eating right now, rather than in the future) 2) "Do I have to wear a suit" is the most acceptable of the three, and can be used both formally and informally. "Have I got to wear a suit" is also correct, but is more informal. "Must I have to wear a suit" is incorrect, but you could say "Must I wear a suit" but it's VERY formal, and you'll likely only hear it in old books, or among the upper class. In everyday conversation it would sound overly formal, and a bit silly!

1) a)what is the family going to eat. this is true. you should use 'be going to' or you can say 'what is the family eating' this is also for future meaning. 2)must i have to.... this is wrong. you can use one of them. Must or have to. Do i have to.... this is correct have i got to wear ... this is also correct but this is for American English.

1) b 2)a