What must be true of a bill which has become law at a federal level?

Question

It must have been signed by the president
It must be in the best interest of all Americans
It must have passed both the house and the senate***
It must have been introduced into the senate before the house.

Answer 1

Correct. The president's signature is usually required, but a presidential veto may be overridden by both houses of Congress.

Answer 2

So it is It must have passed both the house and the senate

Answer 3

Yes.