What is the value of a 1778 US 2 dollar bill?

Answer 1

If the bill actually has that date it's almost certainly a copy.

If it's green and has a picture of Thomas Jefferson on the front, please look at it more closely. The date 1776is shown on the back of the bill because it's the year that the Declaration of Independence was signed and the bill depicts a part of Trumbull's famous painting of that event. The bill's series date is on the front, the same as all other US bills and will be 1976 or later. In that case it's only worth $2 if you got it in change.