3)In what ways does the Constitution contradict the Declaration of Independence?

Answer 1

he Declaration contains a set of ideals. The Constitution contains a set of laws. As far as significant differences...

In the Preamble, there is a statement of equality that wasn't in the Constitution until the Equal Protection clause of the 14th Amendment. Also, where the Declaration talks about "Life, Liberty, and the Pursuit of Happiness" the Due Process Clause protects "Life, Liberty, and Property". Those two clauses have been interpreted as being inclusive of each other by the Supreme Court.

The Declaration talks about overthrow of a government, while the Constitution merely provides methods for amending and changing the govt. Different time, different purpose.

Finally, at the end, the Declaration appeals to the "Supreme Judge of the World" to create "free and independent states", while the Constitution holds itself and the federal govt as supreme, overriding the states.

Those are the biggest differences I noticed at a glance.