The Four Answers:

Each one of these practices is symbolic of our slavery, freedom, or both:

1) On all nights we eat chametz or matzoh, and on this night only matzoh!

Slavery : Matzoh was the bread of slaves and poor, it was cheap to produce and easy to make.

Freedom : Matzoh also commemorates the fact that the bread did not have enough time to rise when the Jews hastily left Egypt.

2) On all nights we eat any kind of vegetables, and on this night marror!

Slavery : The marror  (bitter herbs) reminds us of the bitterness of slavery in Egypt.

3) On all nights we need not dip even once, on this night we do so twice!

Slavery  : The salt water into which we dip the  karpas  (parsley or other green veggie) represents the tears we cried while in Egypt. Similarly, the  charoset  (fruit-nut paste) into which the bitter herbs are dipped reminds us of the cement we used to create the bricks in Egypt.

Freedom  : Dipping food is considered a luxury; a sign of freedom -- as opposed to the poor (and enslaved) who eat "dry" and un-dipped foods.

4) On all nights we eat sitting upright or reclining, and on this night we all recline!

Freedom : We commemorate our freedom by reclining on cushions like royalty.

haggadah Section: -- Four Questions
Source: Rabbi Dovid Zaklikowski,