If you mean "Who is the author of the Haggada?" then the answer isn't known. We don't know for certain who compiled it.
Mordell Klein has written: 'Passover' -- subject(s): Jewish art and symbolism, Passover
David W. Rose has written: 'March of Dimes (NY)' 'Passover' -- subject(s): Seder, Passover, Juvenile literature, Holidays 'Passover' -- subject(s): Passover, Juvenile literature
Gertrude Rubin has written: 'The Passover poems'
Ron Wolfson has written: 'The Shabbat Seder' 'Shabbat, 2nd Edition' 'Passover, Second Edition' 'Passover' -- subject(s): Seder, Passover, Customs and practices, Judaism, Spiritual life 'The Passover Seder' 'A Time to Mourn a Time to Comfort (The Art of Jewish Living Series)'
Barbara Balzac Thompson has written: 'Passover Seder' -- subject(s): Judaism (Christian theology), Liturgy, Passover, Seder, Texts
Evelyn Zusman has written: 'The Passover parrot' -- subject(s): Children's stories, American, Customs and practices, Fiction, Judaism, Parrots, Passover
Labor Zionist Alliance has written: 'Passover Haggadah'
Jacob Freedman has written: 'Polychrome Historical Haggadah For Passover'
Balfour Brickner has written: 'An interreligious guide to Passover and Easter' -- subject(s): Christianity, Christianity and other religions, Easter, Judaism, Passover, Relations 'Finding God in the Garden'
Yes.
The first Passover was in Egypt
If by 'author' you mean main character, then that was Jesus. His Father and He decided the details of His 3.5 year and 4 Passover Ministry long before it actually was.